I’ve used shellac before and never had any problems, but this time the shellac seems to dry as soon as it leaves the brush. I mixed a fresh batch of shellac (Garnet flakes) and I load my brush and by the time I finish the first stroke the shellac is dry. I tried adding 1/2 ts of gum turpentine to 4 oz. of shellac but it did not seem to help. Any ideas? Does the commercially available shellac retarder work?
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Replies
IMHO,
It seemed to work when I tried it. It seems to be a type of alcohol. You're in moderate temps, right?
J.
Instead of using denatured alcohol to mix your flakes use Behlen's proprietary solvent. It has enough isobutanol in it to slow the evaporative process.
Frank
It was close to 85 degrees one day but another day was only 72. I thought humidity affected shellac and not temperature. I may be wrong (not the first time). I just bought some Beklen (sp) alcohol and I will see what happens. I always used denatured before with out a problem.
All the different alcohols dry too fast to retard shellac a significant amount.
Commercially available shellac retarders contain various glycol ethers. For example, the Solar Lux retarder contains diethylene glycol monomethyl ether(DM).
Using a commercially available retarder will slow down the evaporation rate and help flow-out. But shellac retains retarders a long time, so you should add the smallest amount needed to get good results. Generally, a half ounce per quart is good.
Paul
F'burg, VA
Archy,
Shellac disolves in solvents other than alcohol. It disolves in turpentine and in lacquer thinners. If you add turpentine to your shellac solution, you will slow down drying. Add lacquer thinner and you will accelerate it.
There was a good article in FWW about varying the working times of finishes by modifying the solvent phase, but I can't locate the issue. I believe that it was within the last 2 years.
Rich
if i recall correctly laquer thinner is a blend of several solvents, including alcohol.
I guess that various formulations contain more or less of the more volatile components.
Rich
The FWW article is were I got the idea to add turpentine to the shellac. It did not appreciably slow down the drying. I am going to mix a new batch using new flakes. The flakes that I used the first time were about 5 years old.
Thanks
I posted a while back how I had mixed shellac in denatured alcohol contaminated with turpentine. It was really a near disaster. Are you guy's sure about this?
Frank
Frank,
NO!!!
I have added lacquer thinner to shellac with no problem. I have never tried turpentine because I have never wanted to slow down evaporation. Are you sure that turpentine was the contaminant? The only contaminant?
Rich
Frank,
I've done some research on the different solvents for shellac and this thread is the first time I've come across the recommendation to use turpentine. To me, it doesn't make any sense, but I'm no chemist. Turpentine is not a solvent for shellac - it behaves much like mineral spirits and naptha. Turpentine is a solvent for wax only and is a thinner for oil (linseed, tung, etc.), varnish, and oil-base paint.
A retarder is a solvent that is compatible with the resins and other solvents in a product, but evaporates slower than the rest so the product will dry slower. Turpentine evaporates faster than some alcohols (like the isobutanol you referred to earlier) and is in a different chemical class as alcohol. Like I said, I can't understand how it can be considered a retarder for shellac. Your previous experience is an example of the harm it can do.
Glycol ethers on the other hand, are compatible with alcohols (along with many other solvents), and evaporate much slower. That's why commercial shellac retarders use glycol ethers. For example, isobutanol, the slowest evaporating of the alcohols, evaporates 350% faster than DM. Although compatible, they still come with the recommendation to use as little as possible because they have an adverse effect on the shellac film once dry. They cure out of the film very slowly.
With the rapid evaporation rate of the primary alcohol used in denatured alcohol, ethanol, it also doesn't make sense to add lacquer thinner to shellac. When is denatured alcohol ever too slow? What effect does the lacquer thinner have on the shellac? I haven't found any references on this - no authority on shellac I have come across recommends using lacquer thinner. I have found limited literature on the effects the different alcohols have on the shellac once cured - some alcohols are better than others.
From what I've learned, I will not add turpentine or lacquer thinner to any shellac I plan to use.
Paul
F'burg, VA
Can someone quote from the FWW article about using turpentine? I can't find my copy with that article.
Rich
Rich:
The article you are looking for is in Fine Woodworking October 2001 Issue 151 titled "All about thinning Finishes by Jeff Jewitt. On page 88 there is mention of using Turpentine to retard shellac.
I would like to say one thing Rich, listen to Paul. Paul has helped me with a lot of my finishing questions and problems. Paul is an expert finisher who knows and understands finishing. I personally do not brush shellac, I use a detail spray gun for small jobs and a larger gun for large guns. Have never had problems with applying my shellac. I start off with a lb.. cut and do not apply more then a 2lb. cut. I build up the layers until I am satisfied with the results. I mix all my shellac and do not buy pre-mixed shellac.
God Luck:
The old Timer
Chandler AZ
Rich,
Like I said in the post to Frank, I can't understand how turpentine can be a retarder for shellac. It's evaporation rate is higher than isobutanol and propanol but a little less than ethanol (6%). It's definately NOT a solvent for shellac.
It's like the folks on some forums who say odorless mineral spirits is a retarder compared to regular mineral spirits when their eveaporation rate is almost identical - that doesn't make sense to me either.
I will ask Jeff about the turps, as he definately has a better understanding of the chemistry than I do.Paul
F'burg, VA
Rich,
I posted a question about turpentine on Jeff Jewitt's dicussion board. Here's his reply;
"...In formulation of finishes, evaporation is generally calculated using the boiling point of solvents. Turps is around 160 d C, ethanol is 78 d C.
While turps is not a solvent for shellac, it is soluble in ethanol, which is why it works as a retarder. It also has a slight "oiliness" to it, which makes it brush out better."
The Bottom Line - In small quanity, turpentine can be used as a retarder for shellac.Paul
F'burg, VA
Paul and Frank,
I had hoped to use some turpentine with shellac this weekend. Couldn't get to it. I wonder what Frank's adulterated shellac mixture was that didn't dry if Jeff says this will work?
I do believe that his article said that shellac disolves in turpentine, but memory fails. Can anyone confirm? At least he is now saying that it doesn't and it's the alcohol/turpentine solvency (is that a real word) that works. Interesting.
Rich
I think one has to consider the cut, a 1 lb cut is going to dry much faster than a 4. when i filling with pumice i use a thick gooeu cut so i have time to scrape excess off.
I think you're onto something here, wondering about the cut (ratio of shellac to alcohol). In my limited experience, I've found that a 1 lb. cut (less shellac per volume of alcohol) dries much faster to a hard state than a 3 lb. cut (more shellac per volume of alcohol), which gets "gooier" or gummier almost right away, although it takes longer to dry to its final hardness.
Perhaps the miscommunications are around the meaning of the term "dry." Is the problem that the shellac is drying to hardness too quickly, or becoming too gummy too fast?
Personally, I prefer to work with multiple layers of a 1 lb. cut. I've had no trouble with it drying too quickly during the brushing-on process, and on those occasions where I do miss some build up, the coat is thin enough to be easily sanded back to the level of the rest of the finish.
DavidHmmm... the garden or the workshop today?
I think that you are right. When I did all of the trim and doors in my last house I used canned orange shellac. It is a 3# cut. When I did the mantle in this house I did not measure the flakes and alcohol but the mix was relatively thick. This time I measured for a 1# cut and that maybe the problem.
Rich,
I remember Frank's post when he got the "bad" can of alcohol. I'm guessing that there was way too much turpentine mixed in - the description of the mess Frank got when he used the shellac mixed with this stuff sounded pretty bad.
I think the oil in the turps could be a real problem if you use too much. I would also add the turps to pre-mixed shellac and make sure any left over is labeled.
Another responder on Jeff's board says he uses turps all the time becasue he likes the way it flows when he brushes it.
Paul
F'burg, VA
Paul,
Thanks. I have never needed to retard shellac. And the tip about better flow with a little turps is interesting.
Rich
Paul, I've been following this thread because I also sometimes have a problem with shellac drying too fast when I try to apply it to surfaces larger than about 1 square foot. The remedy I've always used is to come back after the shellac is dry and sort of "French polish" the brush marks out with a rag dipped in alcohol. It works, but it's an awful tedious job. I've never tried turpentine as a retarder and, since I haven't kept the genuine (pine distillate) stuff on hand in years, I'm curious about whether mineral spirits (ordinary petro based paint thinner) will also work. Did Jeff say it had to be real turpentine?
I have had good luck putting in n-Butanol in about a 10% add to my 2#mix. I have noticed about a 1/3 reduction in drying time.
Since you had success before, I wonder if it could be the cut? Any chance a 2# become a 4# by some mistake? I find I have to be really careful mixing.
FWIW,
John
Hi Jon,
I didn't ask about the mineral spirits, but I was wondering the same thing. Once again, I could kick myself for the lack of chemistry education. I wouldn't try it without asking someone like Jeff Jewitt or Russ Ramirez (at woodfinishingsupplies.com) - they have the chemistry know how.
Paul
F'burg, VA
Jeff Jewitt's book on Great Wood Finishes mentions the use of turpentine to retard the drying of shellac. It has to be the genuine stuff; he uses about 1 ounce per quart of shellac. I've never tried it myself.
Thinning the shellac should slow down the drying.
Interesting thread! I'm on my first half gallon of 2# cut shellac. I love the clairity and reflective properties of shellac, I've been using the "ultra blonde" color, from flakes. I brush the shellac on with a decent Purdy brush. I've tried a dab of boiled linseed oil as recommended from Michael Dressner to level out the brush marks, slow the drying rate. To be honest I can't tell any difference. I'll be interested in reading other folk's cures for leveling out shellac.
What the heck. We all have scraps lying around. Is is often a good idea to experiment on scraps. Maybe I 'll try Jewitt's mix and see what happens.
I always have some angst about departing from tried and true finishing techniques. I only make 2 or 3 pieces a year and I worry I am going to screw up 30 or 40 hrs work.Perhaps this is not the best way to learn?
Frank
I use shellac frequently. I also read the artical mentioned and tried the turpentine "method" it didn't work for me so I went back to spraying or rubbing on sellac.
Philip
I guess I don't really understand why fast drying is a problem. If your padding just put more on the rag or fill the brush a little more. Afterall, it is easy enough to sand out between coats if it gets too thick. Isn't rapid drying one of the main benefits of shellac?
I haven't had any problems but my shop is in the basement and it is rarely over 75 degres F or <50 % RH.
Frank
It is drying too fast. I load the brush and after a 1' stroke the start of the stroke has started to set. Its hard getting an even finish. I'm doing the doors and trim in my house. I did this on my first house, a 1929 bungalow with red oak trim and doors finished in orange shellac (golden oak). I had no problems. This house is a 1931 bungalow with birch trim and a darker finish. I'm using garnet shellac. I previously had refinished the fire place mantle with out a problem but now I just can't get it to work. I am now mixing up a new batch and have order a retarder. I'll see how it goes.
I am afraid I don't know what else to say. Would cooling the room help?
Frank
ArchyII: I am going to mix a new batch using new flakes. The flakes that I used the first time were about 5 years old.
Have you done this yet, Archy? Did it solve your problem? My best guess is that 5 year old flakes were the original cause of your problem. The do have a limited shelf life - about 1 year when stored under the best conditions.
I thought I have heard that flakes have an almost unlimited shelf life.Gretchen
Shellac flakes can last a very long time if you store them in a cool, dry place. If they go bad, they will not dissolve.Paul
F'burg, VA
Read my post #14 to Rich, it was meant for you.
Good luck:
The Old Timer
Chandler AZ
Before I apply shellac I like to give the piece a coat of boiled linseed oil, wipe off the excess and apply the shellac right away. The primary reason I use the oil is to bring out the grain and figure of the wood. It seems to have the added benefit of keeping the shellac from drying too fast. I was talking to Phil Lowe about this and he felt like the oil gave the shellac better resistance to water and alcohol marks from drinking glasses. Anybody care to speculate on that?
Brandon
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