In my researches on the rediscovery of the old Italian violin varnish, it was essential to use only materials that were available during the years 1550 to 1750 when Stradivari, the Amati, the Guarnerei, etc. produced their masterpieces. For example, clay, wood ashes and madder root were the primitive sources for some of their raw materials. (1) But such sources are not satisfactory in modern times. One violin maker wrote that he tried to prepare an extract from clay and placed it to dry on the roof of his house. He reported his results in this manner: “And then the rains came.”
It may be helpful to summarize the progress and the improvements that have been made after eleven years further research since my book was published and to describe modern adaptions so that violin makers can use them more readily. The scientific and chemical background should be explained. For the sake of brevity, it will be necessary in the following formulas and discussions to refer to portions of my book. (2)
The original principles concerning the composition and the preparation of the varnishes remain valid and have been confirmed by analyses of old Italian varnishes. (3,4,5) Linseed oil and the metal rosinates remain as the fundamental ingredients; however, boiled oil is now preferred because of its better wearing quality and because clear films are obtainable with the resins to be described in this article. (See pages 56 and 57). The oil may be boiled over a small amount of umber in which case ageing for clarification is necessary. The ratio of oil to resin remains three to two.
Some changes have been made in the preparation of the metal rosinates which impart improved properties to the varnishes.
(1) Preparation of Rosin Solution.
275 cc’s Water (distilled preferred).
13.8 grams Potassium Carbonate (c.p. K2CO3)
30.2 grams Gum Rosin (ww grade)
300 cc’s Cold Water for chilling
Dissolve the potassium carbonate and the rosin in 300 cc of water by boiling in a liter Pyrex beaker. This requires a few minutes depending on the size of the lumps of rosin which should be clear, pea to nut size. Boil for five minutes more. Add 300 cc of chill water and make to 600 cc final volume.
The substitution of potassium carbonate for potassium hydroxide (Preparation 1, page 38) may not appear important at first glance. Potassium rosinate is formed in both instances. Moreover, the foregoing formula is very similar to Preparation 8 on page 49; it differs only in the amount of potassium carbonate; this gives the incidental advantage that the time for the rosin to dissolve is greatly shortened. The explanation for the change can be understood from the chemical reaction:
K2CO3 plus Rosin
KHCO3 (Potassium Bicarbonate) plus Potassium Rosinate
The formulation of the potassium bicarbonate is important in the precipitation of the resins which will be explained later.
(2) Preparation of Precipitants.
100 cc 5% Aluminum Chloride Solution (AICI3 H2O)
30 cc 5% Calcium Chloride Solution (CaCl2)
Five percent solutions are prepared by adding 5.0 grams of each salt separately to each 100 cc water. The foregoing mixture contains nearly equal amounts of aluminum and calcium.
Calcium chloride has been added to the precipitating solution because analyses of old Italian varnishes disclosed the prese4nce of calcium compounds, and further research has shown that their inclusion is desirable when used in conjunction with other metals; the use of calcium rosinate alone in the varnishes was not found satisfactory. (Preparation 31, page 84). The formation is of colored compounds from aluminum and calcium with alizarine is still not thoroughly understood (6) but the combination does yield lightfast colors.
Since calcium chloride is now present in the precipitant, alum, a sulfate, should not be used because of the formation of insoluble calcium sulfate upon standing. This is the only reason that alum, recommended in the book (pages 34, 39, 50 etc.) is now replaced by aluminum chloride.
(3) Precipitation of Resins.
100 cc’s potassium rosinate Solution (above)
60 cc’s Al-Ca Precipitant (above)
The two solutions are mixed whereupon a white precipitate is formed. This is treated according to Preparation 2, page 39. In fact, the precipitate contains a form of aluminum rosinate. The completeness of the reaction may be tested with blue litmus paper which should turn red.
When the precipitant is added to the potassium rosinate solution, normal metal rosinates are NOT formed. (See page 50). Instead, it has been found that basic metal rosinates result, perhaps A1(OH)(rosin)2 because of the presence of potassium bicarbonate. This is desirable because the resins are harder and the varnishes in which they are used are less affected by moisture. After the book was published, reports were received that varnishes, made from rosin solution according to Preparation 1, page 38, became soft and tacky in hot humid weather. This defect is eliminated by these modified resins.
Some violin makers question the use of rosin varnishes. This discussion should explain that rosin does not appear as free rosin in the final varnish resins but is combined with metals. The undesirable properties of rosin (high acidity, for instance) have been removed. Aluminum, iron and calcium rosinates are different from unreacted rosin for varnish making purposes.
Alizarine will be used to color the orange and red varnishes and the amounts to be used have been indicated in my book; the two percent suspension is still used and is added to the potassium rosinate solution in which it dissolves readily. Iron compounds remain as the coloring agent for the brown varnishes and the amounts of iron salts to impart various shares of brown have been outlined. However, iron chloride (FeHl3 6H2O) should now be used because ferric alum is also a sulfate and should not be mixed with calcium chloride in water solution.
The working life of the resins may be extended by storing them in a tightly stoppered bottle in a refrigerator. Turpentine remains as a satisfactory solvent for the varnishes in the proportions suggested in the book; however, it has been found that a solvent called dipentene imparts better “brush ability” to the varnishes because of its slower evaporation rate.
The varnishes, together with the preliminary treatment of the wood with raw linseed oil, produce a finish for violins, violas and cellos that is surpassingly beautiful and worth the time and effort to prepare it. And the violin maker who does use it will have the deep, heartwarming satisfaction that the finish is one that the old Italian masters might well have used.
(1) Michelman, Joseph. “Scientific Monthly”, Vol. 81, No. 5, November 1955, pages 221-223.
(2) Michelman, Joseph. “Violin Varnishes”, Cincinnati, Ohio. (1946).
(3) Michelman, Joseph. “Journal of the Franklin Institute”, June 1949, page 569.
(4) Letters, Karl. “Farbe and Lack”, July 1952, page 293.
(5) Michelman, Joseph. “Science”, September 22, 1950, page 337.
(6) Ciba Review, No. 39, May 1941, Page 1418 and others.
Variations of the varnish receipe described below have been around for the last four hundred years. As I understand it, it started out being known as “Fioravanti’s Red” in Bologna, Italy around 1564, and was mainly used by artists. It wasn’t until the early 1700’s that this oil paste was diluted with turpentine and used for violin varnish. Since that time, ingredients have been added to, and then taken away from the original formula.
In 1904, George Fry’s book, Italian Violin Varnishes, referred to this receipe as “Formula No. 11.” In 1934, American violin maker David Coll suggested the use of Venetian Turpentine in place of Greek pitch to give the varnish a deeper red color. Some time later, the French added Sandarac to the recipe, while cutting back on the amount of Venetian Turpentine used.
Unlike “1704”, Formula 411 varnish can be used on new instruments. The color is a beautiful golden red. If there is one drawback to this varnish, it is the drying time. The instrument must hang in direct sunlight for four or five days between coats.
A word of caution: DO NOT MAKE THIS VARNISH IN THE WORKSHOP. THIS VARNISH MUST BE PREPARED OUTDOORS!
FORMULA 411 VIOLIN VARNISH RECIPE
74 ml.: Varnish Makers Linseed Oil (74 ml. = 2 ½ oz.)
150 ml.: Venetian Turpentine
Glass Stirring Rod
70 gm.: Gum Rosin (WW Grade)
½ Liter: Gum Spirits of Turpentine
Glass Jar w/Screw on Lid
Cast Iron Pot (2 Quart)
Mix 74 ml. Of the Linseed Oil and 70 grams of rosin in a two quart cast iron pot and place on the hotplate set on high; stir constantly with glass rod. As the oil and rosin are heated, the rosin will melt and begin to smoke, giving off a strong, pungent odor. When all the rosin has melted, set the timer for fifteen minutes and stir in 150 ml of Venetian Turpentine a little at a time. Continue stirring until the fifteen minutes has elapsed. Remove the pot from the hotplate and allow the varnish to cool for five to seven minutes. Dilute the varnish with the turpentine until you have the consistency for use with a brush. Stir for five minutes. Store in a glass jar with a screw on lid. The varnish is ready to use.
NOTE: This varnish has a shelf life of about one year. Should the varnish thicken, it can be thinned with a small amount of turpentine.
Reprinted with permission.
While many other varnish producers emphasize a system, we prefer to think of our primer, ground, and varnishes as a platform for you to manipulate as you see fit to achieve your ideal color, transparency, and texture. For this reason, we produce the most transparent and color rich varnishes possible using metal rosinates and bottle them with no added solvents or driers. This way, you can use it right out of the bottle to great effect, or you can thin it with the solvent of your choice and incorporate whatever pigments you wish. It can be applied by hand, padded, or brushed to suit your preferences. It is our hope you will enjoy applying it and be pleased with the results.
Suggestions for Use
Use of the Tintura Veneziana primer: After preparing your wood surfaces as you prefer, apply full strength with a lightly charged brush as evenly as possible. Some overlapping strokes are not an issue. Brush with the angle of the figure in maple and other hardwoods, and with the grain on spruce. If your spruce is particularly low density, brushing it first with distilled water may produce superior results. It is strongly recommended to brush the neck with the Primer as well. Being water based, this will raise the grain. As a result, you may wish to burnish with horsetail (equisetum) after the coat has dried. After applying, allow it to dry in the sun or UV box. If you want more color, add another coat. Typically, one to three coats is just right.
Use of the Oleo-Resinous Ground: We recommend a strong tan or application of our Tintura Veneziana primer to induce color and enhance chatoyance before grounding. Taste will dictate what you consider “enough”. After tanning or priming, apply the ground to the entire instrument with a lint free cloth, rubbing vigorously in order to encourage the ground into the upper few microns of the wood surface. Buff off any remaining ground from the wood surface and allow it to cure in direct sunlight or a UV cabinet for a full day. Repeat this procedure until the point where the wood surface is sealed, but stop short of building a film – typically two to three applications is sufficient. If you do perceive a film building, knock it back to the sealed wood surface with solvent on a cloth before proceeding. You may dilute the ground somewhat if desired to enhance penetration, but we feel it is offered at an ideal consistency to penetrate just enough but not too much.
Use of the Varnishes: As with any finish, experiment with it before using it on an instrument. Once you have arrived at your ideal method and look, you can confidently apply it to your work. Regardless of what application method you choose, please ground/seal the instrument with the method of your choice before applying our color varnishes. We recommend our Tintura Veneziana and Oleo-Resinous Ground, but protein and mineral approaches are compatible as well.
For brushing – if applying at full strength, use a stiffer brush. The varnish is very self leveling and will not show significant brush marks. Those that remain can be polished out once the film is cured, if desired. If you prefer to brush a thinner varnish, use a softer brush (we recommend gold taklon) and dilute to your desired consistency with the solvent of your choice. We recommend our Thinning Agent, a blend of dipentene and essential oils, but you may use whatever non-polar solvent you prefer.
For applying by hand or padding – use full strength and apply evenly, padding excess varnish away with the ball of the thumb or cosmetic sponges. Sparing use of our Thinning Agent can make this slightly faster and offer a smoother texture.
Regardless of the application method, we recommend polishing between each coat with a very fine abrasive, such as tripoli or rottenstone, in linseed oil. Then, wipe off any remaining oil and abrasive with solvent on a cloth. You may now proceed to the next coat knowing that the microscopic scratches you’ve created in the polishing process will allow the next coat to integrate with the previous completely.
Curing – Like all oil varnishes, our finishes dry through a combination of polymerization and oxidation. Ultraviolet light, whether from the sun or an artificial source, is key to expediting this process. The time it takes a coat to dry will depend on the strength of your UV source, but a well applied thin coat of our varnish should be tack free and ready for another coat after a full day of sun or 24 hours in a UV cabinet. As with any oil varnish, full curing is a lengthy process that continues well after an instrument leaves your shop. Nevertheless, you can get most of the way there by drying each coat well before adding another and by giving the instrument a few extra days of exposure after the last coat before polishing and set-up.
Again, thank you for your business. We are very happy to be offering unique products to the trade. If you have any questions or would like help or suggestions on its use , please reach out to Jackson at firstname.lastname@example.org.
The recipe below is a well known varnish recipe. It makes a beautiful golden spirit varnish. It is especially good for touch up, as well as for new instruments.
45 gm. Seedlac
7.5 gm. Elemi
200 ml. Alcohol
9 ml. Spike Lavender Oil
Place all the ingredients in a glass container with a lid and let it dissolve. Stir or shake the mixture twice a day until the seedlac is dissolved. There will be insoluble material left on the bottom of the jar i.e. dirt, twigs, insect parts etc. This process may take several weeks. When completely dissolved, heat in a double boiler for several minutes. Let the mixture cool and then reheat again for several minutes.
USE CAUTION WHEN HEATING AS THE ALCOHOL IS VERY FLAMMABLE!
While the mixture is still warm, filter through a fine cloth to remove the insoluble materials. After the varnish is filtered and cooled it is ready for use. The varnish may be thinned with alcohol if it is too thick.
Store the varnish in an air tight container.
Eugene Holtier Varnish
Before varnishing, the instrument has to be prepared: tanned, primed, stained, darkened, etc. and sealed.
1. Mineral Ground Application
a) First Coat
• Mix clear varnish with pumice using a glass muller to incorporate the powder
into the varnish.
• Apply it on the instrument using a stiff brush for scroll and rib joint with the
plates, and spread it evenly with a 3MTM white pad on the large surfaces.
• Let it sit 10‐15 minutes, then rub the excess using square pads of dock fabric.
• Remove the excess ground carefully from scroll crevices and rib plate joint using
a dry, stiff brush.
• Rub the instrument with the dock fabric until you get a nice, burnished look.
• Let it dry overnight in the UV box.
b) Second Coat
• Second coat can be applied following the first ground coat procedure or you can
add brown varnish in the mixture to start building color on the instrument. Let it
dry overnight in the UV box.
2. Ground Application with No Mineral
The ground for spruce (top)
• Rub clear varnish onto spruce top in a circular motion.
The ground for maple (back)
• Mix clear varnish with brown varnish and test the intensity on a sample of the
same wood prepared the same way as the instrument.
• Adjust the intensity of the color based on the contrast desired on the maple
• As on the top, rub a thin coat of the color mixture in a circular motion.
• Let this coat dry overnight in the UV box.
• Repeat the same steps for the second coat. Use a very thin layer application.
3. Varnish Application
For the first coat, use brown varnish. The coat should be thin, applied on the scroll and rib
joint with a synthetic stiff brush (acrylic paint brush).
For larger surfaces, use fingers in a circular motion or tap with your palm. You may also use
the printing method with a piece of prosthetic foam.
Run your fingers across the grain on the spruce top to accentuate the winter growth.
Let it dry overnight in the UV box.
Follow the same procedure for the next coats of varnish, eventually mixing clear varnish into
the brown if you think the instrument is getting too dark.
A coat or two of clear varnish applied at the end will build film and depth on the surface.
Generally, the working time for the varnish at room temperature is about 4‐5 hours.
4. Adding Color
Eugene Holtier Varnish has an intense, transparent and beautiful brown and requires no
additional color. Yet at times, you may find the need to add color in order to achieve certain
Rosinate is highly recommended for its indisputably superior quality. Solvents such as
Lavender Spike Oil must be used with rosinate to dissolve it and maintain the clarity of the
High quality pigments and oil paint such as those made by Kremer Pigments and
Winsor & Newton can also be used.
Be careful, as different pigments/oil paints vary in opacity and translucency. Generally, the
most transparent colors should be used for violin varnish application. Winsor & Newton’s
Alizarin Crimson, Madder Brown and Indian Yellow are good choices to compliment the color
of the varnish.
The finishing should be done after a few days once the varnish is cured. To finish, mix Tripoli
(#51‐3730) with Rubbing Oil (#52‐3900). Apply the mixture on a soft cloth and rub the
varnish lightly using a circular motion. Buff it with a dry, clean, soft cotton cloth.
These are general guidelines. We are sure that in time you will find other ways to use Eugene
Holtier Varnish and obtain excellent results.
• Varnish viscosity can change with temperature. To decrease viscosity of varnish, use
warm water to gently heat the bottled varnish.
• In the event you have a weak UV box, you can add a catalyst. We recommend
manganese catalyst, which dries uniformly. Experiment with how much catalyst you add,
usually a few drops is enough. Too much catalyst can compromise the varnish.
• Catalysts are toxic!!! Always wear gloves when you add a catalyst to the varnish.
• When a bottle cap is hard to open, warm it with a hair dryer. It will help loosen up the
• Use odorless Turpenoid® or any petroleum‐based solvent to clean varnish or applicators.
• Storage – Keep the varnish bottles away from heat, flame, and direct sun. Seal tightly
when not in use. Store in a dark, cool place.
Eugene Holtier Violin Varnish System Usage Guidelines
Gold Color Wood Primer & Reflective Rosin Ground
The Gold Color Wood Primer and Reflective Rosin Ground are a way to prepare and treat the wood of a musical instrument prior to coats of varnish. The more attractive this layer, the more effective any varnish will be in enhancing the natural beauty of the wood.
Before application of Gold Color Wood Primer, wood should be carefully prepared and ready for the primer and rosin ground coats. Many makers tan the instrument in a humidified UV box or exposure to direct sunlight in climates that aren’t too extreme and damaging to the instrument.
Carefully scrape and finish all surfaces with equisetum (horsetail) or something equivalent to this classic technique. The primer has a water base and will raise the grain considerably, so if less texture is desired be sure to pre-wet the wood and flatten the texture with the horse tail finishing once it’s dry.
Can be used under oil or spirit-based varnishes.
Use caution and minimize exposure to fumes and direct contact with the skin. Since these are chemicals which if used incorrectly can be harmful, be sure to follow standard safety
precautions. Protect the eyes, skin and lungs.
Gold Color Wood Primer Application
1. There are various ways the Primer can be applied, but an efficient technique is using
small, rectangular pieces of household sponge. A 1” square or slightly rectangular piece
works well, since it will easily fit in the ribs. When applying to the instrument, the amount going on the wood can be controlled by how much force is used on the sponge. A small, soft bristle brush should be available to apply primer to areas on the scroll, peg box and f-holes and a larger one can be used on the body if preferred.
2. Mineral spirits or high-quality turpentine can be added to the spruce just prior to Primer application to reduce the “wicking effect” on the end grain. This can cause an uneven, darker area from the primer. Use great caution to apply coats evenly and not to “reload” areas that appear dryer. Each application of the primer makes the wood darker so be sure the even coats are dry between applications. After the first coat you can expose to UV light for several hours to see how even and intense the color is becoming. Additional coats can be made until you are satisfied with the result. Be sure to expose to UV with additional coatings to check color intensity.
3. 2-3 coats of Gold Color Wood Primer are sufficient to get a desired, rich golden color. It’s not necessary to apply additional coats of mineral spirits, etc. but still be careful to apply even coats, avoiding lap marks. Rubbing or brushing at a 90-degree angle will help blend any lap marks. This gives the wood a realistic look of aged wood which will augment the beauty of the Reflective Rosin Ground and varnishes applied later.
Reflective Rosin Ground Application
1. The Reflective Rosin Ground is a clear liquid which has very low viscosity and brushes
easily. A medium-soft bristle brush works best. One which is ¾”-1.0” works well for violins and violas, and a larger one for cellos. The synthetic, clear acrylic handle brushes are popular and easy to find at an artist supply. To avoid too heavy a coat, after brushing on the Rosin Ground dry the brush with a lint-free material and even out the coating with this dryer brush. Blend in the areas where there may be extra thick overlapping of the rosin ground.
2. Allow the instrument to dry sufficiently (preferably overnight in the UV drying box).
When dry the wood should still look very porous even though it will be “sealed” from colored varnishes soaking in too aggressively during subsequent coatings. A second coat can be applied if it looks insufficient. If this film coating gets too thick, filling the pores
and showing a very shiny surface, turpentine can be used on a lint-free cloth to remove the excess material. If you are antiquing the instrument a second coat may be replaced with a protein barrier coating, such as egg white which has been whipped and allowed to
settle in a bowl.
1. Mineral Ground Application
a. First Coat. Mix clear varnish with pumice using a glass muller to incorporate the powder into the varnish. Apply it on the instrument using a stiff brush for scroll and rib joint with the plates, and spread it evenly with a 3MTM white pad on the large surfaces. Let it sit 10-15 minutes, then rub the excess using square pads of dock fabric. Remove the excess ground carefully from scroll crevices and rib plate joint using a dry, stiff brush. Rub the instrument with the dock fabric until you get a nice, burnished look. Let it dry overnight in the UV box.
b. Second Coat. Second coat can be applied following the first ground coat procedure or you can add brown varnish in the mixture to start building color on the instrument. Let it dry overnight in the UV box.
2. Ground Application with No Mineral
a. The ground for spruce (top). Rub clear varnish onto spruce top in a circular motion.
b. The ground for maple (back). Mix clear varnish with brown varnish and test the intensity on a sample of the same wood prepared the same way as the instrument. Adjust the intensity of the color based on the contrast desired on the maple flame. As on the top, rub a thin coat of the color mixture in a circular motion.
c. Let dry overnight in the UV box. Repeat the same steps for the second coat. Use a very thin layer application.
1. For the first coat, use brown varnish. The coat should be thin, applied on the scroll and rib joint with a synthetic stiff brush (acrylic paint brush). For larger surfaces, use fingers in a circular motion or tap with your palm. You may also use the printing method with a piece of prosthetic foam. Run your fingers across the grain on the spruce top to
accentuate the winter growth. Let it dry overnight in the UV box.
2. Follow the same procedure for subsequent coats of varnish, eventually mixing clear
varnish into the brown if you think the instrument is getting too dark. A coat or two of
clear varnish applied at the end will build film and depth on the surface. Generally, the
working time for the varnish at room temperature is about 4-5 hours.
3. Adding Color. Eugene Holtier Varnish has an intense, transparent and beautiful brown
and requires no additional color. However, you may find the need to add color in order
to achieve certain desired shades. Rosinate is highly recommended for its indisputably
superior quality. Solvents such as Lavender Spike Oil must be used with rosinate to
dissolve it and maintain the clarity of the varnish. High quality pigments and oil paint
such as those made by Kremer Pigments and Winsor & Newton can also be used. Be
careful, as different pigments/oil paints vary in opacity and translucency. Generally, the
most transparent colors should be used for violin varnish application. Winsor & Newton’s
Alizarin Crimson, Madder Brown and Indian Yellow are good choices to compliment the
color of the varnish.
4. Finishing. The finishing should be done after a few days to allow the varnish to cure. To
finish, mix Kremer Tripoli Rotten Stone Light (#599930) with mineral oil. Apply the
mixture on a soft cloth and rub the varnish lightly using a circular motion. Buff it with a dry, clean, soft cotton cloth.
These are general guidelines. We are sure that in time you will find other methods to use Eugene Holtier Varnish and obtain excellent results.
• Varnish viscosity can change with temperature. To decrease viscosity of varnish, use
• warm water to gently heat the bottled varnish.
• In the event you have a weak UV box, we recommend using our catalyst, which dries uniformly. Experiment with how much catalyst you add, usually a few drops is enough. Too much catalyst can compromise the varnish.
• Catalysts are toxic!!! Always wear gloves when you add a catalyst to the varnish.
• When a bottle cap is hard to open, warm it with a hair dryer. It will help loosen up the cap.
• Use odorless Turpenoid® or any petroleum-based solvent to clean varnish or applicators.
• Storage – Keep the varnish bottles away from heat, flame, and direct sun. Seal tightly when not in use. Store in a dark, cool place.
Unlike shellac, which when mixed with alcohol will dissolve, most varnish resins must be “run” or melted, sometimes at temperatures approaching 600 degrees Fahrenheit, and then mixed with hot oil to form the varnish. This means the safety of you and your space are a top priority. This really is more dangerous than cooking French fries. For higher temperature varnish-making, I move my work station outdoors.
Some oil-resin recipes call for only modest heat, while others require extreme heat and the utmost care in handling the materials. A portable hot plate (not an open flame) works fine. I use a sand bath setup, using a cast-iron cooking pot filled with enough play sand to push in my Pyrex mixing beakers to heat my ingredients. Putting a cold jar into hot sand will probably shatter the jar, so heat everything together from cold. Make sure to use heat protective clothing, eye protection and gloves that can withstand spills of scorching hot oil. If possible, handle the hot jars with beaker tongs or something similar.
Here are some of my favorite varnish recipes. All temperatures are in Fahrenheit, and, yes, you can use a meat thermometer, although I use a digital kiln thermometer myself. Other tools you will need include a thrift-store coffee grinder for pulverizing resins and a metal stirring rod.
One of the simplest old varnishes is to take one part of powdered mastic added to an equal part (by weight) of raw linseed oil, and slowly heat until the resin melts completely. It should not take much heat to accomplish this, so warm slowly and stir regularly; stirring does not have to be continuous. Once the heated oil dissolves the mastic resin, remove from the heat, add one part of turpentine or mineral spirits, and the formulation is complete. This varnish dries pretty slowly because there is no drier, but it performs well even if it does yellow a bit with age.
A little more complex formulation is two parts ground copal heated in a clean jar in the sand bath until it melts at about 600 degrees. Watch carefully and do not heat past the point where it is all melted. Add this molten copal to one part of hot (400 degrees) linseed oil and stir them together until it all cools down to about 150 degrees. Then add two parts Venice turpentine. When the mass has cooled, thin with mineral spirits or turpentine until it acts like you want. If it dries too slowly for your needs, add a teaspoon of alum or a dash of commercial “Japan drier” to speed up the hardening process. Sometimes I put a dab of lead white artist’s oil paint into a jar of varnish to make sure the reaction goes well.
An even more complicated varnish is one part pulverized amber and one part pulverized copal each in their own jar, melting in the sand bath. These must be heated until they melt or “run” at about 600 degrees. Do not overheat. As soon as they melt, they should be added to a jar of four parts raw tung oil that has been cooked (350 degrees) for three hours in a clean jar. (I drape a piece of metal window screen over the ingredients as they are cooking to keep dust and insects out.) Like the previous recipe, add one part Venice turpentine when the soup is warm. Again, once the mixture is complete, I add diluent and drier to suit my particular need.
And finally, here is my interpretation of the historic Vernis Martin recipe that was touted as the ultimate varnish 200 years ago. There are a couple of versions of this recipe in the historic literature, and quite frankly neither makes perfect sense to me, so here’s my take on the subject: Take four parts Venice turpentine, eight parts of powdered amber, and one part powdered copal, and cook them together at about 350 degrees until the concoction is homogenous (30 minutes or so). At this point it will probably be a cloudy soup with the consistency of heavy syrup. Crank up the heat in your sand bath to about 600 degrees and watch carefully to see when everything melts and the solution becomes honey-clear, then turn off the heat. Once the solution cools just a little, add one part hot linseed oil. When cooled completely give it a test drive, and add diluent and drier as needed. Historically the drier of choice would have been lead white or litharge, a red lead pigment.
Making and using oil-resin varnishes takes a bit of preparation and practice, but it can yield an attractive, robust, historically accurate surface that makes it worth the effort.
Casein Lime Paint
100 parts by weight Casein (powder)
100 parts by weight Slaked Lime (calcium hydroxide)
800 parts by weight Chalk
1 part by weight Borax
Mix the powders together thoroughly. The combined powder can be stored indefinitely in this form and water added when needed. Once water is added, it must be used right away. To prepare the paint, add 50 parts by weight of water to 100 parts by weight of the combined powder with constant stirring. Continue stirring until the mixture is smooth and free from lumps. Next, cover the mixture with a thin layer of water and let stand for half an hour. Add more water until a workable paint is obtained of about the same consistency of house paint. It should be used without delay, as it will set hard in a relatively short time, becoming unfit for use in about twelve hours. Color pigments can be added to this mixture to make a wide variety of tints. Simply add an amount of pigment and reduce the chalk by the same amount.
Casein Borax Paint
15 parts by weight Casein (powder)
100 parts by weight Cold Water
5 parts by weight Borax
25 parts by weight Hot Water
50 parts by weight Chalk
15 parts by weight Pigment(s)
Place the casein in a bowl and pour in the cold water. Let it soak for at least one hour. Stir the borax into the hot water in a saucepan or pot until dissolved. Stir the casein solution until smooth and free from lumps. When the casein solution is smooth, add the borax solution to it with stirring. Heat this mixture to 82° C. (180° F.) using a double boiler for a maximum of 15 minutes then allow it to cool. Gradually sift in the chalk, mix until smooth and let stand for half an hour. Add the pigment and adjust the thickness of the paint by adding more water. It should be used without delay, as it will set hard in a relatively short time, becoming unfit for use in about twelve hours. Color pigments can be added to this mixture to make a wide variety of tints. Simply add an amount of pigment and reduce the chalk by the same amount.
Casein Borax Paint (For Artists’ Use)
15 parts by weight Casein (powder)
100 parts by weight Cold Water
5 parts by weight Borax
25 parts by weight Hot Water
Place the casein in a bowl and pour in the cold water. Let it soak for at least one hour. Stir the borax into the hot water in a saucepan or pot until dissolved. Stir the casein solution until smooth and free from lumps. When the casein solution is smooth, add the borax solution to it with stirring. Heat this mixture to 82° C. (180° F.) using a double boiler for a maximum of 15 minutes then allow it to cool. Pre-wet your pigments with water and add the cooled casein solution to the pigment until you have the consistency you desire. Thin this paint with water for use.
As with all water-based paint, the pigment has to be wetted first. This is done by adding small amounts of water to the dry pigment. Using a palette knife or spatula, mix the water into the pigment until it has a paste consistency. Add the casein solution to the pigment paste sparingly. The casein to pigment ratio cannot be given in exact proportions. The amount of pigment varies according to the pigment. To test for sufficient binder, apply a small amount of the paint to a substrate and allow to dry. If the pigment comes off after a gentle rubbing, add more casein solution. Once pigment and binder have been combined to the desired consistency, the resulting paint can be thinned with water.
The shelf life of casein is indefinite if stored in a cool, dry location.
Procedure for Running a Hard Copal
Weigh a metal beaker preferably of stainless steel or stout aluminum with a stout glass rod to be used as a stirrer and a thermometer reading to 360 deg C. If a metal cased thermometer is used you can dispense with the stirring rod. Place in the beaker 100 g of the copal broken to about ¼ in. size. Fix the beaker firmly and heat it outside. Heat slowly so the resin in contact with the walls of the vessel does not char. Keep the mass moving and note the temperature at which it becomes pasty and decomposition begins. As the mass becomes more liquid the rate of heating is increased. Note how the liquid runs off the stirrer, also the temperature at which frothing subsides and a quietly boiling liquid, which runs freely off the stirrer is obtained. This is the point at which, in making a varnish, oil can be added. The loss from the heating will be in the range of 25-35%. Cool the run copal to 275 deg C. and add slowly with stirring an equal weight of Varnish Makers Linseed Oil heated to 160 deg C. From time to time note how drops cloud when allowed to cool on a glass plate. Continue to heat and stir until a drop remains clear on cooling. This is the point at which the mixture can be thinned to make a satisfactory varnish. Turn off the heat and allow the mixture to cool to 140 deg C. Add turpentine (approx 30-40 ml) to thin to the desired viscosity. NOTE: During the running process there is some risk of fire. It can be easily extinguished if the heat is removed and the vessel is covered quickly.
Ferrous sulfate, also known as green vitriol, is available as a light green powder or crystal. A good stock solution can be made by dissolving two ounces in one quart of water. Small amounts of the stock solution when diluted with water will produce lighter shades.
Ferrous sulfate stains wood by reacting with the tannin present in the wood. It works best on woods that are high in tannin such as oak, walnut, mahogany and cherry. It works to a lesser extent on woods such as maple, birch, cedar and beech. It will produce silver-gray to steel blue colors depending on the strength of the solution and the species of wood. Prestaining woods that are low in tannin with a solution of tannic acid will produce results similar to woods that are naturally high in tannin.
Ferrous sulfate can also be used in conjunction with logwood extract to produce an ebony stain. To one pint of boiling water add one ounce of ferrous sulfate and ½ ounce of logwood extract. Apply this to the wood while it is hot. When the surface has dried thoroughly wet it with a solution composed of seven ounces of rusty nails dissolved in ¼ pint of vinegar.
You should experiment with the stain or dye on scrap wood until you obtain the desired results.
Potassium dichromate is a reddish orange crystalline material. A good stock solution can be made by dissolving four ounces in one quart of water. Small amounts of this stock solution when diluted with water will produce lighter tones.
Potassium dichromate stains wood by reacting with the wood itself. Mahogany is one of the woods affected most strongly by potassium dichromate. When sponged with a solution the wood becomes a dark, rusty red and the contrast between the light and dark markings becomes more accentuated. The color produced depends in part on the type of mahogany used. On Cuban or Spanish mahogany the effect is more pronounced than on Honduras or Philippine Mahogany.
With potassium dichromate oak can be stained a dark rusty brown. Maple and birch are stained a soft yellow. Other colors can be achieved by applying a prestain before applying the potassium dichromate solution. Two prestains that can be tried are tannic acid and logwood extract.
Other effects can be achieved by adding potassium dichromate to a water soluble aniline dye and applying the resultant solution.
Generally, speaking, there isn’t a stain or dye that can be guaranteed to produce a certain color unless all the facts are known regarding the wood used. Even then the results are not certain. You should experiment with the stain or dye on scrap pieces until you achieve the color you are looking for.
Potassium Permanganate is a dark purplish-violet chemical that is readily soluble in water. One or two ounces dissolved in a quart of water will stain most hardwoods a pleasant brown. If the color is too dark it can be lightened by washing the wood down with a solution of sodium thiosulfate (also known as hypo). A solution of potassium permanganate loses its potency on standing so prepare a new solution each time.
A handsome lasting walnut color can be obtained by preparing a solution of six ounces of potassium permanganate and six ounces of magnesium sulfate (Epsom salts) in two quarts of water. The solution is applied hot to the wood with a brush and the application is repeated once.
Use caution when working with potassium permanganate as it is a strong oxidizer.
In 1500, when Pedro Álvares Cabral and his crew, having been blown off course en route to India, chanced upon an unfamiliar shore Cabral prudently claimed the land for the Portuguese Crown and ordered his crew to take on board examples of flora and fauna that showed commercial potential. Brazilwood, botanically known as Caesalpina echinata (often known simply as “brazil”) is a tropical hardwood of the family Leguminosae whose core yields a brilliant red pigment ideal for dyeing cloth. Brazilwood is a creamy color when first cut, but once it has been reduced to sawdust and soaked in water for several weeks, the dyestuff leeches into the solution and can be used to produce the fashionable red clothing particularly favored in the French court. Although the name is of uncertain origin, “brazil” is thought by some to be derived from brasa, the Portuguese word for a red-hot coal or from the Arabic word braza, meaning bright red. More likely the term was adopted from the common name for an East Indian dyewood called “bresel wood” which was first imported to Europe in the Middle Ages. Dyers of old used brazilwood as an additive to heighten the color of madder, or as a cheaper substitute for cochineal.
To extract the color from the wood 4 ounce wood chips should be placed in a cheesecloth bag or nylon stocking and let soak in 1 gallon of water for 1 week. After soaking , cover and bring the chips and water to a boil, and let them boil vigorously for 1 hour.
Brazilwood extract is used in a manner similar to logwood extract. When used with the following mordants it will give these colors; Potassium Dichromate, red to maroon; copper sulfate, pink to red; ferrous sulfate, gray to black; alum, crimson; and tin, pink. When vinegar is added to brazilwood extract the range of colors shifts to scarlet to rust colors and with baking soda the colors are shifted to the blue and magenta colors.
A large number of substances, quite different from one another in composition and properties, and which have no common properties except their red color, have been erroneously classified as Dragon’s Blood. The true Dragon’s Blood is the product of the Calamus draco, a Malay palm allied to the rattan with a stem bristling with sharp spines. This climbing stem may rise to a considerable height. It is not cultivated, and only the trees growing wild in the forest are exploited. The resin exudes from the fruits. The C. Draco bears a great number of rounded fruits the size of a cherry, the surface of which is covered with smooth imbricated scales. The surface on maturity of the fruits are covered with a layer of friable red resin. The fruits are then collected, beaten in sacks to detach the resin, which is sifted to separate the fallen scales. It is beaten in boiling water and kneaded into ball’s (Dragon’s Blood olives) or in long thin cylinder’s (Dragon’s Blood in sticks). These are the most esteemed. The fruits that have been used in the preceding operation are crushed and boiled in water; the resin that they contain floats to the top. It is separated and made into cake’s (Dragon’s Blood in cakes). The ligneous residue that has been boiled is kneaded into balls and sold as common or lumps Dragon’s Blood. Contrary to what one might believe, it still contains a comparatively high proportion of resin. Good Dragon’s Blood is dark red, opaque and friable. Its fracture is red and brilliant. Its odor and taste are scarcely appreciable. Its powder is red vermilion and slightly soils paper. It is insoluble in water and almost completely soluble in alcohol, benzene, chloroform and carbon disulfide.
This yellow gum resin is produced by several species of guttiferae of the genus Garcinia, a genus comprising numerous species of tropical evergreen trees. These species are Asiatic, being more particularly native to Indochina, Siam, India and Ceylon.
Indian gamboge is the gum resin secreted by the Garcinia Morella, an evergreen tree of the forests of the Kasia hills, Eastern Bengal, the West Coast and Ceylon. The gamboge of European commerce comes from Siam and is obtained from Garcinia Hanburyii. This tree grows not only in Siam but in Thailand and all Indochina. Gamboge has been known since ancient times. Clusius was the first European writer to mention it in 1605, Chinese books refers to it in the thirteenth century. The gum resin is not collected to any extent in India, that country receiving its main supply from Thailand. The trees are ten years old before spiral tapping, which is done during the rainy season, when sap is vigorous. The spiral is cut around the trunk 10 feet from the base. The resin trickles down into hollow bamboo’s and when left for a month or so to solidify. The bamboo joints placed over a hot fire crack and a round stick of gamboge is obtained from each, the roll or pipe gamboge of commerce. The best samples of pipe gamboge are of a brilliant pale yellow when rubbed with the moistened finger. It is dense and brittle like glass. Its fracture is conchoidal, smooth, and shining, and of a reddish-yellow color, which soon changes to liver color, the surface becoming coated with a dark green layer. It is odorless. Its taste is slight at first, but it produces an aftertaste in the back part of the palate or throat that is unpleasantly acrid. The streak is lemon-yellow changing to orange. Its powder is a brilliant yellow, but it is less dark than the surface of the section. Mixed with water gamboge forms a beautiful yellow emulsion that is used in watercolor painting. It dissolves completely when treated successively with alcohol and ether.
Gamboge contains, according to the kind, 35 to 80 per cent of yellow resin and 14 to 19 per cent of gum soluble in water. The resin consists of gambogic acid and may be separated from the gum and impurities by dissolving in alcohol. By evaporating the alcohol pure gambogic acid is obtained as a deep brown-red color when pulverized becomes converted into a beautiful yellow.
Gamboge is very soluble in ether, less soluble in alcohol. It is often adulterated with starch, sand, and tinctorial barks, a fraud that is detected by dissolving the finely ground resin in 60% alcohol and examining the residue with a microscope. Gamboge as met with on the market varies greatly in quality. Gamboge from Ceylon, a pseudo-gamboge, is said to be very inferior.
Gamboge is used to color golden lacquers but, it is not very light fast. Moreover, it is poisonous, being a drastic purgative. Pigments have been made from gamboge by converting the resin acids into metallic gambogiates.
Gamboge can be used as a ground color on violins. There are two different theories though as to what should be used. Some say the materials that dissolve in alcohol should be used and others say that the residue that remains should be used. The solution can be prepared by placing the gamboge in alcohol and letting it sit for several days and shaking it each day to help it dissolve.
Logwood, also known as Campeche wood, is the heartwood of a South American tree (Haematoxylon Campechianum). It is a small many trunked tree that was named by the Spaniards who discovered it on the shores of the Bay of Campeche in Mexico. Logwood was introduced to Europe in the 16th century and was especially prized because it could produce a good black with an iron mordant. The dye is found in the heartwood of the tree. It is usually available as chips, powder or in extract form. It is used with various chemical mordants to stain wood various colors. Depending on the mordant used logwood will yield blacks, grays, violets and blues.
To use the extract dissolve one ounce in one quart of hot water. This will give you a dark red to purple solution. Applying this solution, while hot, to the wood with a sponge or brush is best although it can also be applied when cold. Let the wood dry for 24 hours. Now brush or sponge on a solution of one of the following mordants, depending on the color desired. For grays and blacks use ferrous sulfate, for blues use copper sulfate, for lavender use alum, for purple use tin chloride, and potassium dichromate generally gives a blue toned charcoal color. To develop the purple color using tin requires the use of Cream of Tartar. Mordant solutions are prepared by dissolving two ounces of mordant in a quart of water. After applying the mordant solution let the wood dry for 24 hours. If the color is not dark enough another coat of the mordant can be applied.
To prepare a good dye using either chips or powder, it must be soaked overnight and then boiled vigorously about 30 minutes. The liquid is strained out; this is the dye. More water can be added to the wood, as further boiling will extract more dye. In formulas calling for one ounce of extract use two ounces of chips or powder.
The following are some example formulas using logwood. Other information and formulas can be found in “Adventures in Woodfinishing” by George Frank and “Woodfinishing” by F.N. Vanderwalker.
Ebony Stain – To one pint of boiling water add ¾ ounce of ferrous sulfate and one ounce of logwood powder. Apply this to the wood hot. When the surface has dried thoroughly, wet it with a solution composed of seven ounces of steel filings dissolved in ¼ pint of vinegar.
Ebony Stain – In one quart of water boil ¼ pound of logwood powder, subsequently adding ½ ounce of potassium carbonate, after strainings apply the mixture hot. Then again boil the same quantity of logwood in the same quantity of water, adding ¼ ounce of copper sulfate and ¼ ounce of ferrous sulfate, after which strain and put in ¼ pound of rusty steel filings. With this latter mixture coat the work, and, should the wood not be sufficiently black, repeat the application.
Weathered Oak – Boil together 4 ounce of logwood powder and three ounces of ferrous sulfate in 2 quarts of water for 40 minutes and the solution applied hot. When this has dried it should be gone over with a wash made from 4 ounces of steel filings and 1 pint of vinegar. The steel filings are previously put into the vinegar and allowed to stand for several days. This will penetrate into the wood very deeply, and the stain will be permanent.
Rosewood – Boil ½ pound of logwood powder in 3 pints of water. Continue the boiling until the liquid assumes a very dark color, at which point add 1 ounce of potassium carbonate. When at the boiling point stain your wood with 2 to 3 coats, but not in quick succession, as the latest coat must be nearly dry before succeeding with the next. The use of a flat graining brush, deftly handled, will produce a very excellent imitation of dark rosewood.
Mahogany – Rub the wood with a solution of potassium carbonate, ¼ ounce to one quart of water, and then apply dye made by boiling together 4 ounces of madder root and 1 ounce of logwood powder in two quarts of water.