Anyone know if it’s ok to put a coat or two of shellac over poly for the color effect, then finish it with nitrocellose lacquer?
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Replies
I've put lacquer over a shellac sanding sealer before without any problem, but I've never tried shellac on poly. You can always do a test, but I have a few questions:
Why is the poly there? I guess maybe it's already there and you want to change the color of the piece. But if it's raw wood, it seems like you don't need the poly.
Why shellac and lacquer? Nitrocellulose lacquer was developed as an alternative to shellac. You can always tint the lacquer and skip the shellac, or just use the shellac and skip the lacquer. Not sure why you want to use both...
Technically it will work. Aesthically, hmmm. I don't think you'll like the results. That's the strangest sequence of finishes I've heard.
Scuff sand the poly as evenly as possible after it's well-cured. Shellac will adhere to anything. NC lacquer will have no problem bonding to the shellac layer.
Rich
edit: Pondfish, you posted while I was thinking about this and tinting the lacquer was what I was going to suggest. I agree - tint the lacquer, forget the shellac.
Edited 9/17/2006 9:57 am ET by Rich14
Thanks for the responses.
The poly is already on the wood. The shellac is for the sake of the garnet color. Since I don't have a sprayer, the NCL will be sprayed from a can so I can't tint it. I suppose I can get by without the benefit of the shellac color....how well with the NCL go over the existing poly?
Any other ideas?
Let me suggest that you could use a phenolic resin varnish like Waterlox Original Gloss or Satin and get virtually the same coloration as you would from the garnet shellac.As to applying lacquer over an oil based varnish, you must let the varnish fully cure for at least a month but six months is better. The solvents and thinners in lacquer can cause the varnish finish to crinkle unless the varnish is fully cured. Be careful if the varnish finish is relatively new.What's the reason for the lacquer? As others have said, your schedule is almost the direct opposite of what most would use.Howie.........
I hadn't thought of Waterlox Howard...good idea. Especially after seeing "Ruffturn's" jewelry box on WN last week. Do any major chains carry that stuff? Thanks everyone!
Edited 9/17/2006 9:15 pm ET by Knotscott
Some Ace Hardware stores carry Waterlox, but the ones near me that do only have the "original" in stock and need to order the gloss version. None of the big box stores carry any Waterlox finishes that I am aware of.
For those interested, Woodcraft has a fair Waterlox selection. So far, I like it alot.
You can use Zinsser Seal Coat right out of the can to adhere to almost anything, and almost anything adheres to it. Seal Coat is a completely dewaxed clear shellac in a 2# cut. It has tremendous sealing capabilities -- even to the point of stopping sap stains or color bleed.I suggest you use it first, then top it with the garnet shellac. Can't really see any reason to coat over the shellac. It is pretty tough once cured. I have used it on floors.
Unless you spill your martini on it...
Yes, that's true. Shellac does not like alcohol. If it is wiped up quickly, no problem, but if it remains a while, there could be a problem.
J
We just had Don Williams (Senior furniture conservator at the Smithsonian) in town doing a lecture and then a hands-on workshop. To say hes a fan of shellac would be a gross understatement. After the workshop I think I may do my next project in shellac.
Interesting. What were his main reasons for liking it?
Joe
I think its long term stability was the biggest reason. Reversability and repairability were other reasons I can remember. I beleive the control and options it offers him are big plusses. His reason for disliking polyurethane, for instance was that it starts changing in as little as 3 years.He said in no uncertain terms that penetrating oils should NEVER be used as a maintenance cleaner / restorative. It darkens the wood, can polymerize the finish, attract dust into the finish etc.(I *really* hope I'm not misquoting him - remember, he's made no warranty on any of the dumb things coming out of *my* mouth).
Makes sense. I am not an expert, but have studied it a bit, used it extensively and had correspondence with Zinsser's tech staff on various things. Here are the plusses I think I know:
Stable, including reasonably UV stable
Easy to apply
Easy to clean up
Non-toxic
Fast drying
Seals very tightly (no sap or paint bleed through)
Can be used to seal woods for more even stain application (like, say, Pine)
Easy to repair (just clean the surface and apply 2# dewaxed coat after which you can apply another coat of whatever shellac you are using.
Environmentally friendly, renewable, non-petrochemical substance (made by insects, actually)
Tintable with a variety of pigments
Drawbacks
Not hard enough for heavy duty use, such as commercial floors
Alcohol IS its solvent, so spilled alcohol can damage the finish
I am not aware of a matte or satin shellac product, so those finishes require extra steps
Oh, Don also suggested not using Denatured alcohol. He prefers to use as pure an ethanol as possible (except when he wants to retard the drying of the shellac when he'll use something like propanol)
I have never noticed a difference in shellac's properties based on denatured vs "pure" ethanol as its solvent. I believe denatured is a mixture of ethanol and isopropyl, and that's proprietary to whatever manufacturer you get it from, with whatever poisons the manufacturer puts in there to make it unsuitable for human consumption.
Isopropyl and turpentine will slow down evaporation a bit for use in wiping or padding. Since I spray it, that's not a factor I worry about.
What is the advantage of using ethanol vs denatured?
Rich
>>What is the advantage of using ethanol vs denatured?The primary advantage I can see for use denatured ethanol is that you don't have to pay huge excise taxes on the denatured stuff. "pure" ethanol, i.e. food grade, would include in it's price federal, state and sometimes county excise taxes. By "denaturing" the alcohol, making it unfit for human consumption, you no longer are required to pay the excise.
Jim,
I agree. That's why I asked about that recommendation to use ethanol. I am not aware of any disadvantage to using the denatured variety. Some folks even recommend using the laboratory-grade stuff which costs a freaking fortune.
I just buy the denatured at the Big Box and I'm happy (as far as disolving shellac).
Although shellac is my favorite finish and an absolute delight to use in every way and probably the finest material available in the known universe with which to finish wood, having gotten pretty proficient with a number of lacquers, I tend to use them more.
Rich
Rich14
I'm certainly glad to know that it's not critical to use denatured alcohol. I've a buddy who loves to make moonshine.. He's not much of a drinker and refuses to sell it but would rather give it away... (to his friends.) When I visit him I always bring him sacks and sacks of sugar. When I leave the truck looks like a moonshine car all lowered down on the springs..
In the past I've always handed it out to friends of mine, now I'll use it to mix with shellac flakes..
Hey anybody know a source for them in bulk? The only place I can find them is the wood working shops and they always want 16 prices for stuff..
I've got a giant timberframe to shellac and could use the price break over buying from Home Depot.
I wish I could remember why he said denatured alcohol was bad. I think it also depended on what it was denatured with;
If the ethanol was denatured with propanol he said that was okay, but he did say that alot of alcohol was denatured with "rocket fuel" (whatever he meant by that) and that stuff he said was lousy...Anyhoo.
I think alcohol is denatured with benzene. Benzene being pretty nasty stuff for human consumption. But I think the quantity is very small.
Here are some denatured alcohol MSDS sites:
http://www.syndel.com/msds/denatured_ethanol_msds.html
http://physchem.ox.ac.uk/MSDS/DE/denatured_alcohol.html
http://www.sciencestuff.com/msds/C1156.html
Apparently the main denaturing chemicals are methyl alcohol and isopropyl alcohol.
Frenchy,While your moonshine will most likely dissolve those shellac flakes, I wouldn't recommend it. Moonshine is not going to be 100% alcohol, there will be a significant percentage of water in there. My grandfather, a moonshiner of the old school, would usually triple distill, aiming for 100-120 proof corn squeezin's. For the non-initiate, this is only 50-60% alcohol, not nearly pure enough for shellac.
JimV
You're right!
He did say that it was 120 proof and that I should mix it with regular booze to get the same taste.. If I wanted Canadian Club it should be about 1/2 and half. Same with burbon etc..
I tried drinking some of it and hated the taste plus I got a whale of a hangover from just one glass..
Anyway to get it to 200 proof? (100% alcohol)
Damn, now I gotta climb into the way-back machine to remember that chemistry major I never used after I graduated./LECTURE: OnYes, you could bring it to 200 proof. No, you can't do it in a economically feasible way. From a production basis, you have really 2 ways of doing it:
1) A fractional distillation column. Effective, requires several runs to insure purity, requires extremely careful monitoring of temperatures to be successfull.2) Vacuum distillation. Can be done at room temperature. Requires a significant investment in equipment.However, neither of these methods can bring it past 96% purity, which is the azeotropic point of a ethanol/water mixture. The most effective way of doing this is further distillation of the 96% pure mixture in the presence of benzene. This is known as azeotropic distillation and allows you to distill out the rest of the water. However, then you need to remove the benzene in a environmentally responsible way./LECTURE: OffBasically, use it for engine stripper.JimEdited 9/24/2006 9:41 pm ET by JimV
Edited 9/24/2006 9:42 pm ET by JimV
You don't want to use Moonshine to dissolve shellac. It almost certainly contains much more water than would be desirable. (100 proof is about 50% water.)
The apparent advantage of high grade ethanol is low moisture content compared to big box denatured alcohol. But any such advantage dissappears very quickly once the alcohol is opened since alcohol with pick up moisture directly from the air. (By the way this is a MAJOR problem with the higher ethanol fuels being advocated. Not too much of a problem for cars that use up the tanks regularly, but for marine uses, where fuel can set for some period of time, it can be a disaster. )
Let me add to the list and make a couple of comments.>>Drawbacks 1. Not hard enough for heavy duty use, such as commercial floors
2. Alcohol IS its solvent, so spilled alcohol can damage the finish
3. I am not aware of a matte or satin shellac product, so those finishes require extra stepsActually, shellac is one of the hardest finishes available. But, hardness means it scratches more easily and that's a primary reason that it does not make a good floor finish. Poly floor coverings are much softer and that is what gives them their scratch resistance and toughness. Poly is quite soft as far as finishes go.While alcohol can damage a shellac finish, the alcohol in drinks is not a big hazard. Even if you drink you martini "neat" the alcohol content is only 40%. With other mixed drinks, the alcohol is even less. In other words, you have quite some time to wipe up any spilled before it begins to damage the finish. An even bigger hazard are today's household cleaning products that contain solvents and ammonia. Ammonia rapidly will damage a shellac surface so stay away from things like Windex.Finally, you can buy flatteners to put into shellac that will create a semi-gloss or satin finish.Howie.........
Good points -- tell me more about the flattners. Any particular meterials or brands?
Joe
>> tell me more about the flattners. Any particular meterials or brandsContact Homestead Finishing Products: http://www.homesteadfinishing.com/Good source for shellac flakes also.Howie.........
HowardAcheson,
Anyplace to buy flakes in bulk cheaply?
I hate paying retail for stuff if I don't have to..
Joe,
I'll tell you why I love shellac.. I have a old piano from the 1930's, it's finish was in rough shape...
Decades of neglect and no cleaning thought..
A few hours with a rag soaked in shellac and the finish was off completely..
Bare wood. ready to finish.
I'm a sloppy, lousy, painter.. Runs seem to be my main achievement.. Shellac and by the time I'm finished with one side the other side is dry enough so I can wipe off my runs.. (rag soaked in alcohol again) back to the slopping with a brush..
Three quick coats and it looks better than a 1000 dollar paint job!
Wood floors should only be shellaced as far as I'm concerned.. Repairs take minutes (and if you kept a alcohol soaked rag handy we're talking seconds. Shellac dries to the touch in about 10 minutes and for good in 8 hours..
It has depth without the plastic look of poly's it has a richness that can't be faked and a history almost as old as man..
The original and never beaten finish..
Now maybe some women are squimish about the butt juice of the lac bug but it's wonderful properties more than make up for it..
I agree. The surprising thing is that the shellac is not better known and more widely used.
Joe
Big Frank,
It's also one of shellacs real strengths..
I have a big dog, 150 pounds of Newfoundland. His toenails always seem to need clipping and we seldom get around to clipping them.. when he's excited and jumping around floors get scratched..
Period..
Any other finish and that means hours of sanding etc..
Shellac and you just wipe a rag soaked in alcohol, (brand doesn't matter) and the scratches disappear!
minutes of work instead of hours!
Now every single wood surface in the interior of my house is shellac.. ten minutes a month and no scratches are there!
I just love the butt juice of those lac bugs!
Well, if you can't tint the lacquer go ahead and use the shellac for its color. Either way, carefully take the poly down to an even scratch pattern at about 320 grit sandpaper or 3-0 to 4-0 steel wool for adhesion of either the shellac or lacquer.
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