What do I need to know about shellac?

Repairing an old chair that has/had a shellac finish.

Normally, I can dip a rag in alcohol and reactivate the shellac finish and redistribute it.  But this one doesn't have enough left.  I need to add another layer but it's my first time mixing flake and applying the finish.  I also don't have much expierence with mixing solvents like alcohol.

1. Can I mix it in a metal container like used for turps?  I bought one of these stainless steel containers when I started oil painting but didn't end up needing solvents, so it's brand new and eager to be used.  But all the tutorials call for glass.

2.  What's a good ratio of flake to alcohol for a chair?  It's real, bug shellac.   I don't want it to be so thick that it would take forever to dry.  Some shellac I've seen can stay sticky for months afterwards.  My memory says it's not enough alcohol at time of application.   My memory also dredged up the usual ratio of shellac flakes to alcohol is 1:3 by weight for french polish on a guitar.   But I've seen ratios as week as 1:10 and as strong as 1:2.  What would be good for a chair?

3. Is it worth while applying a second coat?  Wouldn't that just reactivate the first?

4. Anything else I need to know?

I don't seem to have a skin or breathing sensitivity to old shellac, but I'll be working outside anyway.

Hi - I was looking at lac for dyeing and as an aside it said that the shellac part was very reactive with metals which made the varnish dark, and could even eat through any tin containers.  So I guess glass or plastic could be best for mixing/storage.

I can only help with question 3 with any certainty. I can add something to the "anything else" too. I bought pre-mixed shellac.

I absolutely feel that it is worth doing a second coat. Technically it may reactivate the first coat a little... but the reactivation takes time, and if the first layer is dry, the second layer doesn't mess with it too much, and then dries with a thicker finish that will stand up to wear and tear better than a single coat.

Then, I would personally say stay away from dyed shellac because of one experience that may or may not be related to the dye. I've used shellac for quite a few wood projects. I would always buy the pre-mixed without dye and I would work on the project... set my brush aside and let it dry. Then the next project would come along, and I would put the brush in the can, and let it soak for 30-60 minutes, which would soften he brush up and let me do my next project. However, one time they were out of what I normally got, and I found another product by the same company that said all the same stuff... except it had color. When I did the same thing with my brush, it dried hard, and I went to soak it for about 30 minutes. It had not softened at all. I let it soak another hour, still no softening at all. I ended up leaving it soaking for probably 5 hours and it never softened. I ended up having to get a different brush. So I now avoid any dyed shellac. Your mileage may vary.

Not sure on dealing with wood that has already had an existing coat.   Going back to a shop class I had ages ago, apply a second and third coat. Sand in between coats with fine sandpaper. Do not sand the final coat. BUT this applies to new finishes.

I didn't realize they sold pre mixed shellac.   I never go down that aisle.

It's very tempting!   Anyone know of a no/low toxic brand?  The appeal of mixing my own is i know the ingredients.  

I have used Zinsser Bulls Eye Clear Shellac. It claims to be all natural, and the Internet claims they do in fact make it from the excretion of that beetle. Other places say that it is a combination of real and synthetic. I suspect it's less bad than most, but I can't back anything up.

**Edit - Went to their site and now maybe the amber is the better option vs clear because they bleach it to make it clear? See second picture of their description.
**Another Edit - here is the full PDF on their products. https://www.rustoleum.com/-/media/F7350AC8AA7E4787A1287F1E775BA1CC.pdf

Matt McSpadden wrote:I have used Zinsser Bulls Eye Clear Shellac. It claims to be all natural, and the Internet claims they do in fact make it from the excretion of that beetle. Other places say that it is a combination of real and synthetic. I suspect it's less bad than most, but I can't back anything up.

Nifty
Thanks for the suggestion.

Their safety data sheet lists these as the dangerous ingredients

alcohol, denatured 64-17-5 NotSpec
isopropanol 67-63-0 NotSpec
methyl isobutyl ketone 108-10-1 NotSpec

The last one I don't know.  Looks like the main risk is to breath it.

Looks like our local worksafe doesn't feel it's one of the more dangerous solvents but it sounds a bit like saying the drowning risk is less in a swimming pool than an ocean.  

I'm going to put this one high on my list of possibilities, but keep looking for an option that would require less fuss to dispose of the rags and stuff.

Alcohol of various kinds is a well-respected solvent and sanitizer. (I'm not talking about the "social lubricant" use of ethyl alcohol.) I've never heard it described as dangerous except around flame.

A few months ago I did some studying on shellac, and finished a new wood spinning wheel.

I decided on mixing and dissolving undyed flake in everclear, a food grade 95% ethanol product.  A big factor in that decision was the shelf life difference between commercially prepared and home prepared shellac.  There’s a time limit (several months) after which home mixed shellac should be discarded.  There is not a similar discard date on the commercial products (that I could find).

Being a suspicious sort,  my simple mental process was this: “What are they putting in to- or what are they doing to - the commercial shellac to get the shelf life.  Why is that not being disclosed?  

I was going to do the french polish method but a spinning wheel has a lot of surface area and I wanted to complete the project.  And I figured that any time I wanted I could go back and rework the finish.  I don’t know if that would be possible using the commercial products.

As for refinishing the old chair, I would probably wipe it down with everclear.  If the surface wasn’t the condition I wanted to preserve, I would lightly sand it, then apply the flake- everclear dilution.  As for mixing proportions, I think maybe mixing test batches and applying to a wood scrap , or the bottom of the chair might give you the best idea of the differences on the finished product of the different dilutions.

Just generally, I think a dilution with larger alcohol to shellac ratio would penetrate the wood deeper and with multiple coats, make a sturdier finish.  It’s how they finished musical instruments in the old days.  A Stradivarius violin probably was finished with shellac, using a thin dilution and multiple coats.

I think more shellac flake and fewer coats could come off more easily.

If you mix your own, you’re supposed to strain it.

Have fun with it, the mix it yourself is a very forgiving product.

Ah.. it's the word alcohol.  

We usually use Methyl alcohol (also known as methanol or wood alcohol) is the simplest alcohol, with the chemical formula \(\text{CH}_3\text{OH}\). It is a highly toxic, volatile, and flammable liquid used primarily as an industrial solvent, fuel, and raw material for manufacturing products like formaldehyde and plastics.

Basically, drink this for a fast path to blindness, insanity, and death.  Although, it does seem to be one of the least toxic alcohol solvents.  It doesn't burn skin, doesn't leave a toxic residual, is made from natural sources.

Once we get away from a social setting, alcohol is a word for very specific molecular chains.  Methyl alcohol has the perfect structure for binding to shellac with the lowest amount of residual.

Unfortunately, I can't seem to find it in the shops and now I'm wondering if it's a controlled substance due to people mistaking it for drinking alcohol.  I really don't want to use the major toxic stuff and drinking or medical alcohol doesn't bind to shellac.

It appears ethanol performs just fine in use with shellac.

I may be confused by your terminology. I think of binding as when there’s a permanent reaction between two substances, for example using fiber reactive dyes on cellulose fibers, the pigment and the cotton are molecularly bound together.  To me, dilution is more like the role of water in water color paints, especially the little dry cakes sold in a set, often for children and other beginners.

We’re in different countries, and therefore have different regulatory agencies.  If I wanted to find methyl alcohol here, I would start at the hardware store.  I know they are selling some kind of alcohol solvent in my town. I went with the much more expensive food grade alcohol because I knew I would be breathing it, and though wearing gloves I figured I would likely get some on my skin.  I am kind of messy, (always end up with stained hands when dyeing). But with everclear food grade alcohol there are no unknown additional ingredients, therefore no unlnown hazards.

Anyway, here’s the shellac dissolved in ethanol finish on my spinning wheel

r ransom wrote:...
Unfortunately, I can't seem to find it in the shops and now I'm wondering if it's a controlled substance due to people mistaking it for drinking alcohol.  I really don't want to use the major toxic stuff and drinking or medical alcohol doesn't bind to shellac.

Methyl alcohol isn't hard to find in my neck of the woods, but it's also sold as gas line antifreeze.  Methyl alcohol is also called methanol, methylene, and methyl hydrate.

David Wieland wrote:

r ransom wrote:...
Unfortunately, I can't seem to find it in the shops and now I'm wondering if it's a controlled substance due to people mistaking it for drinking alcohol.  I really don't want to use the major toxic stuff and drinking or medical alcohol doesn't bind to shellac.

Methyl alcohol isn't hard to find in my neck of the woods, but it's also sold as gas line antifreeze.  Methyl alcohol is also called methanol, methylene, and methyl hydrate.

That's what i expected. It used to be used for so many things.  

3 DIY shops, 2 Canadian Tyres (automotive section and paint section), a gas station, one agriculture shop, and a few other shops. I managed to find one person who actually knew what it is at a lumber shop, but they can't get it in.

The closest thing I can find is methyl tetra-something, but that requires fancy gloves (nitrate instead of regular ones) and can leave a nasty residue if spilled, and get into the ground water.  Not keeping with the permaculture style I'm going for.

I'm curious about ethanol working.   That might be easier to find.

A person could also produce their own ethanol…. Ferment their own something or other, then distill the ethanol, or buy some liquor and distill the alcohol out of that… but maybe that’s too long a process to undertake before getting to the chair project.

Thekla McDaniels wrote:A person could also produce their own ethanol…. Ferment their own something or other, then distill the ethanol, or buy some liquor and distill the alcohol out of that… but maybe that’s too long a process to undertake before getting to the chair project.

It's a tricky process and one needs to know their local laws.  It is a lot of work for a chair.  

Buying shellac predesolved might be the solution.

I haven't checked the local shops for ethanol yet.  Something for next weeks shopping..

https://www.leevalley.com/en-ca/shop/tools/supplies/finishing/finishes/76311-shellacs - Under Care & Use is a pdf that tells how to mix & how to apply.  
https://www.shellac.net/Shellac_ordering_list.html - At the top of this page is a link to another pdf , again a good how to.  

Shellac goes off, supposedly, if it sits too long.  I've got a a can of Zinssner from aproject that left about 1/4 leftover & refuse to throw out & I use for tool handles.  I haven't had any of it set up soft or weird.  It's great on plunger handles too!  I won't use it for anything important but it's a good utility sealer.  

Also-  Here's an article about shellac in general & particularly today-  https://christopherschwarz.substack.com/p/the-state-of-shellac

About methanol; I think it's what we would call methylated spirit in the UK, although the concentration and purity might be different. I did find some at Walmart Canada, that looks like it might be available to order online: https://www.walmart.ca/en/ip/DUSTRONICS-Ultra-Pure-Methanol-99-9-4-litre/514J4UMYJ5GK . It is quite a large amount and so quite expensive though. If normal ethyl alcohol works as well I'd go for that, since any you don't use would have lots of other uses in preserving and tinctures for example.

Nancy Reading wrote:About methanol; I think it's what we would call methylated spirit in the UK, although the concentration and purity might be different.

It might be.  We have stuff labeled methylated spirits in the US, but it is not reliably methanol.  I have used this mystery solvent to mix shellac and not had any trouble with it.  But without knowing what's in it, results can be hard to reproduce.  There is no requirement I've ever found dictating that "methylated spirits" must be made from methanol, despite the implication.  Similarly, "denatured alcohol" is not a specific product nor a specific alcohol.  It could be ethanol (with toxins added to make it not a beverage, ostensibly so that solvents are not subject to a liquor tax), it could be made with methanol, it could be made with isopropanol (commonly mixed with water to make "rubbing alcohol").

r ransom wrote:...We usually use Methyl alcohol (also known as methanol or wood alcohol) is the simplest alcohol...

Some light research suggests that ethyl alcohol is the usual solvent for shellac -- but denatured with methyl alcohol.
From a Duck-Duck-Go search assist:
The best solvent for shellac is ethanol, often found in the form of denatured alcohol.

I’m just speculating here that shellac and ethanol both predate the denaturing processof ethanol.  That practice probably came in to practice when taxation of alcohol began.  Then to buy untaxed ethanol for use with shellac, and as solvents for other substances.

I think, based on my speculation, that straight ethanol as everclear or high proof vodka is a workable solvent for shellac…. May have been the original solvent.🤷🏻‍♀️

In my 50+ years experience with various finishes, I have never been disappointed with ANY Zinsser products!
They do sell it in your area.