I’ll start off by saying that we’re not painting contractors.
So, I’ve got some paint-grade maple drawer fronts that we shellaced, in order to seal the wood to prevent any bleed-through, prior to priming. Well guess what: it seems that the shellac was past its shelf-life and won’t dry. This is after three days under a fan.
I tried wiping down the drawer fronts with methyl hydrate (twice) to clean off as much of the tacky shellac as possible. Then, I began to prime the backs with a shellac-based primer, on the advice of someone from Benjamin Moore. It’s not going well. The primer is gumming up and has a very textured appearance. I think the old shellac is preventing the new primer from curing properly.
Yikes. The client is coming back on Tuesday, so I’ve got some time to try and rectify this, but I need a solution soon!
Replies
I tried wiping down the drawer fronts with methyl hydrate (twice) to clean off as much of the tacky shellac as possible.
The solvent for shellac is alcohol, if you want it off try that.
What's the date on the bottom of the can? Where did you buy it?
Joe H
Don't use a fan. It skins over and the solvent can't evaporate as fast. Keep the area warm, instead. Use denatured alcohol instead of the other solvent. If needed, use a heat gun set to low or medium. It's gonna be a long process but it will dry, eventually.
If the shellac is past its useful life it won't matter how long you wait or how much heat you apply--it will never fully cure. (You can tell if the shellac is bad by putting a few drops on a piece of glass or metal. After a couple of hours it should be dried and hard. If it is still tacky or gummy then it is no good and should be tossed.) The only option is to remove the old shellac and start over. As already stated, use alcohol as a solvent and make sure you remove all the old shellac. If you don't and try to finish over it, you will most likely end up with a "crackled" finish. People will pay good money for a specialty finish like this and it is often used to give a painted piece an old or antique look. Maybe you can convince your customer that you decided to give them a customized antique finish at no extra cost?
I double-checked, and "methyl hydrate" is just a fancy term for denatured alcohol. I'm using the right stuff.
I guess I'd better keep plugging away at it. Thanks for the input.
That's a methanol base. Use an ethanol base denatured alky.
Use an ethanol base denatured alky.
Shouldn't really matter - any of the commonly available alcohols is a solvent for shellac, and should be fine for cleaning it off.
Woodturners commonly use rubbing alcohol to mix shellac flakes - it's inexpensive and readily available. If the slight water content annoys you, pure alcohol from the liquor store works very well and has none of the toxic chemicals used to denature alcohol (well, except for the alcohol itself, which is a poison).
"pure alcohol from the liquor store works very well"OTOH, it's impossible to remove all of the water from alcohol, unless the air has been completely dried. 190 proof is about as high as it gets, so 95% pure is is. Cheap vodka might work. Not worth drinking but it's great as a household cleaner. Yes, I'm kidding.
"I cut this piece four times and it's still too short."
OTOH, it's impossible to remove all of the water from alcohol, unless the air has been completely dried. 190 proof is about as high as it gets, so 95% pure is is.
Cheap vodka might work. Not worth drinking but it's great as a household cleaner. Yes, I'm kidding.
I agree. However, rubbing alcohol (isopropyl) tends to have a significant amount of water in it, compared to the others.
I haven't bought it in a while, but I used to get what they called "pure grain alcohol" at the state store. They claimed it was 200 proof (i.e. pure alcohol), but my suspicion based on some informal testing is that it was more like 190 proof. It's tough to get more than 190 proof from a still.
But if you want to make your own, there is a link on one of the popular consolidation sites. Please use it only as a shellac solvent, please do not drink it.
Laboratory grade alcohol has water in it- one of the properties of alcohol it that it absorbs water from its surroundings. It may be 200 proof once, but if it's distilled in atmosphere, it has water in it. A lot of rubbing alcohol has a bit of mineral oil in it, to aid in massages. It can be bought without the lube, though. Weird smelling stuff. Little blue flames, unless there's a lot of it burning, or it isn't pure.
"I cut this piece four times and it's still too short."
Exactly what kind of "informal testing" did you do? Perhaps a bit of a taste test? LOL
Are you the Andy Charron who wrote my book on spray finishing?
Dang, I bet he wrote my spray finishing book, too. Good book. I might have two different ones he wrote.
Billy
That depends. Did you like the book and find it helpful? If so, then yes I am. If you didn't like the book or found it of no use, then I am someone else. Seriously, in answer to your question, that is my book.
I guess you're someone else then...
Just kidding. That book got me up and running with spraying and I refer back to it frequently. I guess you might know a little bit about the OP's question.
Yea, I learned about shellac and "crackle" finishes the hard way. When it comes to shellac my rule of thumb is "when in doubt, throw it out." The cost of mixing a new pail of shellac is cheap when compared to what can go wrong using an old batch.
> Shouldn't really matter - any of the commonly available alcohols is
> a solvent for shellac, and should be fine for cleaning it off.No, methanol is not a solvent for shellac.George Patterson
George,I thought the primary reason to avoid using methanol was safety. Pure methanol is way more toxic than denatured ethanol, which has a small percentage of (most often) methanol.Is it true that methanol won't dissolve shellac? I've never tried it, but I think it would strip the shellac if it didn't properly dissolve it. Stripping is actually what the OP wants for his drawer fronts.Nonwoven abrasive pads, alcohol, good gloves and ventilation, plus elbow grease ought to make rapid work of the gummy shellac.Bill
Methylene is what is a stripper, as In Chloride.Spheramid Enterprises Architectural Woodworks
"If you want something you've never had, do something you've never done"
Sphere,No, I am not confusing the two compounds.When methylene chloride started to be recognized as the health hazard it is, several companies responded with a "less dangerous " stripper formulated with acetone, toluene, and methanol in combination. This combination is basically the same as lacquer thinner.Bill
This certainly has been educational. In any event, the stuff I was using is indeed ethanol denatured with methanol. I wasn't really much in doubt, considering the jug read:"Methyl Hydrate
Shellac Thinner"It seems to have done the trick, guys. I used up a couple liters of alcohol, washing the drawer fronts over and over. After about 90 minutes of scrubbing and wiping, they stopped feeling tacky. An acrylic primer seems to have gone on just fine.Thanks for all the input! This misadventure was quite the waste of time, but it was less frustrating than finding out that the Corian fabricator hadn't even received the raw material on the day they were scheduled to install. And we already ripped out the clients' existing counter. Awesome.
No, methanol is not a solvent for shellac.
Actually, it is an excellent solvent for shellac, and some folks prefer it over the others. Most alcohols will dissolve shellac.
I don't know if you are familiar with Jeff Jewitt, but he is regarded as a "finishing expert". From his web site:
"Alcohol -- There are four suitable alcohol solvents for shellac - methanol, ethanol, propanol and butanol. Methanol is an excellent solvent, but it is toxic, so I avoid using it my shop. Ethanol is far better because of its low toxicity. Butanol has an odor which I find disagreeable so I don't use it as the main solvent. Propanol, the alcohol in rubbing alcohol can be hard to get in chemically pure form but it’s a good solvent for adding to shellac solutions as a retarder. "
http://antiquerestorers.com/Articles/jeff/padding_shellac.htm
Methanol won't work.George Patterson
Bill -
Have you thought of getting new drawer fronts? I know, it sounds like an expensive solution, but you're running short of time and - if I'm understanding this thread - you aren't sure if your efforts to remove the shellac will even work. It might be time to bite the proverbial bullet and take a hit for being a little late rather than busting your hump and then having the job go south anyway.
A quick call to the cabinet maker may solve your problem.
Denatured alcohol will take it off
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Your shellac is undergoing esterification I believe. An acid plus an alcohol reacts to become an ester. (When polymerized, esters become polyester, as in cheesey leisure suits from the 70's.)
The sticky mess you have is incomplete esterification. The strongest and purest alcohol you can find with some elbow grease should clean it up. Anhydrous ethanol would be best but the 190 proof stuff from the liquor store would be the next best thing.
good luck.
I knew I could count on you guys to educate me a little on the chemistry. :-) I'll probably try to find some purer alcohol, maybe. We'll see how it turns out.I can get replacement doors in two weeks, so I'll be late anyway if this doesn't work. I tried washing them over and over for about another hour today, but I had to run and didn't try priming again.
Biff,
I use a lot of shellac, some of it is past expiration and I've found that the higher the pound cut (2# is worse that 1# 3# is worse than 2# etc..) the worse the reaction.. another words straight from the can is never going to dry while a less than 1# cut (or three parts denatured alcohol to one part shellac) seems to dry out the oldest shellac quickly..
You wind up using a lot of denatured alcohol but since it dries so quickly the trade off seems well worth while..
Have you ever used grain alcohol? I read a recent article that suggested using 180 proof everclear
I read that about the chemical reaction with shellac and acid. The acid, IIRC, comes from the metal in the can. That's why it's best to use shellac flakes and store them in an air tight glass jar (or plastic bag) until needed and then mix with alcohol (though it's not as convenient, but neither is shellac that refuses to dry!).