Shellac happens

Re: Shellac happens

DavidChatham

>As far as I know , it is shellac flakes and alcohol.

Shellac flakes are an organic compound excreted by the lac bug. I don't know if modern science has found or bothered to find a way to make this compound. On the other hand, I know a few recipes for alcohol!

Dave

Re: Shellac happens

ThomD

>Well it isn't like H2O, it's alcohol into which has been disolved various amounts of the excresions of the lac beatle. Call CSI and get a DNA workup.

Re: Shellac happens

Stephen in Utah

>Shellac is an organic compound and has a formula like C6H12O6, can't do sub scripts. It is also available in a food grade, called confectioner's glaze, amazing what we eat.

Stephen

Re: Shellac happens

Scott in Douglassville

>Are you looking for the actual chemical formula for the physical excreted shellac? I'd guess that, at best, it'd be an amalgam of all kinds of stuff, varying based on a number of variables (location, season, weather, etc), rather than a discrete compound. Interesting question, though.

Re: Shellac happens

Stephen in Utah

>Yes,

The number of Carbon molecules, the number of Hydrogen molecules, the number of Oxygen molecules, etc, etc, etc, etc of this exudation.

It is a complex enough compound that they have not been able to make a synthetic version.

Stephen

Re: Shellac happens

Scott in Douglassville

>Well, speaking strictly out my rear, I'd opine that it's the subtleties in formulation because of genetic differences in bugs, soil differences for individual trees, whatever polutants were in the rain that fell that year, that change the mix. Dump it all in a mass spec and you'll find out how many Cs, Hs, Os. It's - what'd Dave call it? - the gentle application of chaos theory? - that makes synthesis tough. Or impossible.

Re: Shellac happens

Stephen in Utah

>It is the exact formula of the end product that I am looking for. I hope this discussion is not getting too scatological.

Stephen

Re: Shellac happens

Scott in Douglassville

>Nah - it's discussions like these that make me glad I'm going back to work in chemistry.

I'm curious if you can narrow it down to a discrete formula. I'll be watching to see what comes up.

Scott

Re: Shellac happens

mikew

>CH3CH2CH2(CHOH)(CH2)7CHOH·COOH, i.e., dihydroxyficocerylic acid

However...I would agree that it is likely impossible to reduce all variables and have what we know as shellac. Else it seems it would have been done.

I suppose this is similar to synthesizing other organics. Which while often producing an effective equivilent, isn't the "same."

Have fun--let us know why the quest for the shellac grail if and when you can!

Take care, Mike

Re: Shellac happens *LINK*

mikew

>btw--this was the second hit on a Google search. I have no idea whether it is correct or not!

The link is below...Mike


Shellac linky

Re: Shellac happens-OT

Patrick Gibbons, Houston, TX

>Ersatz shellac is probably not economically feasible now. However, when the economies in places like India and China ramp up closer to American and European standards shellac may be too expensive to use. Also think about how much a cup of tea might cost.

Re: Shellac happens

James Watriss

>Are you talking about Blonde, Amber, Button...?

I have a feeling that you may still find that there are variances in just what makes up shellac. I have a feeling it's an amalgam of various substances, because of the mechanisms involved, and because of the amount of "stuff" that can be processed out as it is refined, and the fact that it has a shelf life, which indicatess to me that there are reactions occuring within the substance itself... either some components are reacting with others, or primary components are breaking down, and degrading.

If it's a process of degradation, you'll have to figure out just what it is tht you're after... the "original" molecule, or the resultant products as it "breaks down" which form the film we all have come to know and respect, if not always love.

Re: Shellac happens

ThomD

>Just as far as the shelac in solution is concerned it normally goes bad because it absorbs moisture into the alcohol, etc... The lac is pretty stable in chip and furniture form.

Re: Shellac happens

James Watriss

>I've had experiences where the chips start to have issues, stick together, don't dissolve quite as well as they used to... might be a moisture absorbtion issue, but still.

Re: Shellac happens

Miles

>Isn't it likely to be what the organic chemists call "Complex Residues and Products" when a synthesis or reaction goes messy and doesn't give a clean product?

I suspect it will be like plant waxes, spermaceti, etc - a predominant component that dominates the overall character, plus a spectrum of other stuff that helps optimise it for the bug's purposes, & who knows what happens to it all when it's refined.

I found this : http://www.newton.dep.anl.gov/askasci/chem03/chem03638.htm which helps explain why it goes off over time.

Question - In my shop class, students learned that shellac solutions

in alcohol will form ethyl ester over time and make the solution unusable.

What is the chemical composition of dry shellac?

What functional groups are present other than carboxylic acids that

convert to esters?

Is there a more appropriate solvent that would avoid this problem?

------------------------------------------------------

I am assuming that you use alcohols to prepare the solutions. If so, then

the reaction is with the alcohol and the carboxylic acids in the varnish.

This is a self-catalyzing reaction (that is the carboxylic acid provides

enough protons to start the reaction) and because the energy required to

get the reaction going is low, it will happen over time.

Greg (Roberto Gregorious)

I also found an old (1938) paper that describes how minor constituents of colophony, for example, prevent crystallisation of the main components, and this is critical to film formation.

From this brief look, the warnings about not using old shellac would seem to have a firm base in the chemistry, if the esterification with alcohol reaction happens to a significant extent. I'm prompted to look at the behaviour of the unbleached vs bleached grades, as unbleached might retain some components that are removed during bleaching, so affecting film forming, polishing behaviour, etc. I don't know if anyone here can comment from experience?

Why

Bill Tindal, E.TN

>Just back from hiking in S. Utah and it is clear that spring has not found your part of the world yet. Colorado was white all the way to Kansas border on Wed. There was no need to take short sleeve shirts on this trip.

Anyway, one could answer your question more usefully if you described why you want to know (how the information is to be used). I pursued this question a while back and found that shellac is not a single compound and that what the bug poops out changes upon processing. However, an empirical formula could be had, and no doubt has been done, by analyzing the material for C, H and O, a simple task.

Re: Why

Stephen Shepherd in the State of Deseret

>I have accumulated a large amount of information about shellac and I am interested in the minutia, the physics, chemistry and properties of this great finish. I at one time had the complete formula which was composed of several molecules. Unfortunately I can not find that exact formula.

Shellac is one of my favorite finish and I use it on a regular basis. When I am asked questions about this I want to be able to answer ad infinitum.

I work at a living History Museum ca 1857 and need to be able to adequately answer questions, and some of them are challanging.

So that is my interest.

Stephen Shepherd

answers

Bill Tindal, E.TN

>the chemistry of shellac is described in detail in "Protective and Decorative Coatings", Gardener and Mattiello, New York 1941; **Yates and Field, Tetrahedron, Vol 26, page 3135(1970) ; Cockeran, Journal Society of Cosmetic Chemistry Vol 12, page 316(1961) ; American Ink Maker, Volume 39, page 26(1961) and another book E. Hicks, "Shellac , Its Origin and Applications, Chemical Publishing Comapny, New York (1961) and **J. Martin in Kirk-Otmer Encyclopedia of Chemical Technology Vol 20 pages 737-747.

The stared ** references are readily obtainable in any university or industrial chemistry library. Others might be harder to get.

Shellac is a very complex substance comprising a mixture of various esters and (poly)esters which vary with the details of the source of the bug poop. I could send copies of some of these references if you can't find them locally. Contact me off line with "shellac" in the subject line. The main components are esters of shellolic acid and aleuritic acid, plus waxes.

The naturally occurring esters seem to be especially reactive. I suspect the action of water is to hydrolyze these esters to their respective acids while the action of alcohol is to convert the original esters into esters of ethanol, either of which would drastically change the properties of the resin. I would think that shellac would be stable in very dry ethanol or other alcohol, or a solvent with out an alcohol functionality.

Re: Why

vlparisian in Houston

>I would think that if you answered most inquires with the resonse that it is bug poop, that would pretty much stop any futher questions and you could get back to your work. ;>)

my $.02

victor

Well, there's your answer...

Scott in Douglassville

>There's no way that the actual composition of shellac was accurately described in 1857. Tell 'em that. ;^)

(Ok, I know that's not a real answer. Chemistry's a funny thing - once you start getting interested in the details, it kind of haunts you. Good on ya.)