I make a point of searching out and buying a 190 proof (95% ethanol) denatured alcohol for making shellac. However many of the denatured alcohols sold at hardware stores contain lesser percentages of ethanol (i.e. a student just asked me about “Sunnyside” brand; the MSDS reveals it is only 86% ethanol). If someone prefers to buy whatever denatured alcohol is available at their local hardware store, at what percentage number does the ethanol in the formulation become too low to be suitable as a thinner for shellac?
Also, the MSDS for Sunnyside’s denatured alcohol lists “hazardous ingredients”, which add up to about 94%. What is the other 6% or so percent composed of?
Thanks
I am not a specialist in “Shellac” but have made many shellac finishes in my Frame Lab over the years and have found numerous examples to formula problems and shellac preparation can vary even to time of year, summer in Washington, DC with high humidity. Your question about denatured ethanol alcohol (methylated spirits) is valid and unfortunately not all Denatured Alcohols are equal and there is no purity standard, if you refer to “Shellac.net” for example you will find that the “percentage of alcohol” sold over the counter will vary greatly and the best being Select 190 proof which can be purchased from H. Behlen & Bro. and Behlen Benkol, shellac solvent. As Brian referred to; The problem is not the alcohol used as to the “water” content in your denatured alcohol, which works as a “retarder” as water evaporates much slower. How one handles their materials is important, I always “decant” all solvents from their main containers, which is my practice in my Conservation Lab. Your question did not refer to what “Shellac” you are preparing as many shellac products vary and some have short shelf lives. For example; in preparing stick-lac, seed-lac and button-lac shellac’s one should use a fine cheesecloth bag, when preparing all others the mesh bag can be omitted. Know that “White Shellac” has a short shelf life and should be discarded. I always run test’s on materials to see the effects before I touch a work of art. Martin Kotler, SAAM 2017
I use the Benkol alcohol, it is very good. And, as you say, I always test out a shellac before applying to a work of art. Thanks for your helpful comments.
Unfortunately, I cannot give you an authoritative answer but I have asked one of our other moderators to comment.
In the meantime, here is my unofficial estimation of what is going on. Most likely, this denatured alcohol is 86% ethanol and 8% of another non-consumable solvent (methanol in England but there are other options) which is used as the denaturing component. The aim here is not to make a poor shellac solvent (really the only general use today of denatured alcohol is for shellac and alcohol burners), but to render the solvent unable to be used as an intoxicant. The remainder is likely water.
I have personally dissolved everything from stick, seed, orange, garnet, and dewaxed blonde shellac in hardware store brand denatured ethanols without problems or precipitation. Shellac is not completely soluble in ethanol of too low a proof resulting in in a turbid, white semi-solution. You can witness the same effect by adding water to a dissolved solution of shellac. The resin will precipitate out of solution when the proportion of ethanol drops too low.
Baade, Brian
2017-02-25 20:25:17
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