Calling Restorers, what is nitro cellulose laquer?

[astrid]

This thread arises out of another, but may help restorers with a common problem, ie how to strip old nitro cellulose laquer.
In my extensive stripping experience, i have found that some laquers, although all soluble with meths or paint stripper, strip differently and some are easier than others. In other words NC's ain't NC's sal
Some go gluggy but are easy if messy,
Some go dry and crusty and harden again fast
Some go white and chalky and are hard to get off.

now a little research tells me that nitro cellulose itself, is a result of vegitable fibre and nitric acid,

nitrocellulose laquer has something added as a carrier but this must vary or we wouldnt have the different results when we try to strip it.

I am talking about the stuff used from 20's to 60's not modern stuff

So what are the different carriers(for want of the scientific word) and can we find out the best ways to strip different types of NC laquer.

If we can sort this it could save a lot of time, energy and help a lot of us generally.

Astrid

[jeffhigh]

Why not just use lacquer thinners or acetone?
That will redisolve nitro straight away.
Maybe add some retarder to give a bit longer working time

[Gra]

On metalwork a good molasses bath strips all paint, and eats the rust at the same time. well it works for us car guys anyway. The main drawback is it eat the rust, so sometimes you don't get much back .

[astrid]

Of course there are other ways to strip it but acetone is too dangerous to use
on large areas on a regular basis, not to mention the cost.
And i imagine molassas (yuk) is only practical in a very big workshop with copious amounts of water and i hate to think what it would do to the wood.

This is a historical research question if you like, It would be interesting to know what different mixes were made and to what purpose and effect.

Astrid

[jeffhigh]

For a good explanation of the solvents for nitro cellulose see
http://www.allprocorp.com/ics/documents/Lacquers.htm
Most importantly, alcohol (metho) is not considered an active solvent and will only disolve NC in the presence of a primary solvent such as acetone or MEK
This would be why you are getting poor results using it as a stripper.

[astrid]

Meths disolves some old NCL beautifully.
if you read my original post again, i have described the different effects meths has in 20's to 50's finishes.
I dident say i got a poor result, I want to know why the effects are different.
I am a proffessional restorer and strip at least 50 peices a year by hand.
I certainly wouldnt want to be using acetone

Your link is most informative but i think it must be refering to modern laquers if it insists that alcohol wont disolve it.

maybe its because the NCL has broken down over time?
I dont know and I want to find out.

Astrid

[jeffhigh]

Hey Astrid, When I said a poor result, I did not mean that you produced a bad end result, merely that You found it more difficult than you would prefer.
My experience is mainly with applying NC rather than removing it
On one piece that I stripped I used lacquer thinners and this remover it very quickly
You experience with metho intrigued me so I tried it on a mid 50s finish. It certainly softened the surface but not as dramatically and as deeply as the lacquer thinner.
I have hear of but not tried lacquer thinner/metho 50/50 for nc removal also lacquer reducer which is less volatile.
The variable effects could be due to breakdown (nc is certainly not everlasting)
Maybe also extent of cracking/wax and silicone residue/ shellac sanding sealer.
I am not aware of changes in nitro other than the addition of plasticisers to some modern products

[echnidna]

Nitro cellulose laquer has been obsolete for many years and not readily available these days. It was replaced by acrylic lacqer which for practical purposes is the same thing.

It redissolves with lacquer thinner.
Though 2 pac lacquer won't redissolve.

Good practice to wear gloves and avoid skin contact with thinners and especially acetone.

[Big Shed]

Nitro cellulose laquer has been obsolete for many years and not readily available these days. It was replaced by acrylic lacqer which for practical purposes is the same thing.

Sorry, have to disagree, nitro-cellulose is still extensively used in eg pre-cat lacquers for the furniture industry.

Companies like Haymes, Mirrotone, Protec and a host of others all make nc based pre-cat lacquers.

See here

and here

[Gra]

And i imagine molassas (yuk) is only practical in a very big workshop with copious amounts of water and i hate to think what it would do to the wood.

only use it outside... Usual is a wheelie bin at the bottom of the garden and close the lid. From memory it was a 50/50 mix with water, but would have to look up the recepie. Just make sure you attach everything to a decent STEEL wire, otherwise you have to fish around in the bottom of a full wheelie bin (That is yuk) As I said it is for metal wouldn't use it on wood, would probably eat it. Also some metals don't cope either (Zinc i think is one)

[astrid]

To economicaly strip NCL with meths, you put a old towel on the surface your stripping. soak it in meths, push out the air bubbles and leave for five minuites.
then it softened completely and you strip with a scraper or gather up the goo with course steel wool depending on the makeup or whatever of the NCL.
as i said, the only time this is harder is when it goes chalky and this could be sanding sealer or even plaster sealer.
thats what im trying to find out
lets just call it womens insatiable curiosity

Astrid

[durwood]

Hi Astrid,

A type of finish is determined by the base resin used in its manufacturer. If I am making N/C I buy N/c resin which comes in bags crushed up to the size of blue metal and I dissolve it in solvent getting a liquid which I then doctor to improve it or alter it for specific purposes. Whats added to it determines how good or bad the quality is. You can even mix it with other resins there was one Japanese brand in the 70's that was a mixture of N/C and Acrylic.

I'm not sure that all the surfaces you are stripping are N/C lacquer. Don't forget there are a lot of other clear finishes around. Especially alkyld enamels, acrylic lacquer and varnishes in many forms. If they react entirely differently to solvent or paint stripper going gluggy as you stated then they would probably be an enamel of varnish type finish.

If pieces of furniture were being refinished from whatever original finish by someone at home its probably a clear enamel product they would be applying from the hardware store as lacquer would require spray painting equipment.

As for the N/C itself there has always been various grades ( qualities) some cheap industrial ones perform terribly compared to the top end ones so the difference in removal may be the fact the metho attacks them easier than the others. All lacquers can be remelted with solvent (enamels/varnishes can't) Thats the beauty of them if you damage them you can just rub them back, apply more lacquer to the area and then use the thinner to melt the edge of the new lacquer into the old to produce an invisible mend. Great for small marks aon large areas.

Jeffhigh's assesment is on the money. Metho is a diluant not a solvent its added to lacquer thinner to extend or water it down. Instead of using a lot of expensive solvent they use small amounts of a strong one and then add cheap solvents such as metho to extend the quantity. When you get cheap thinner you usually get thinner watered down with metho. It works ok but better quality thinner gives a better finish of the gun and often greater servicibility from the product.

Molasses does remove paint but its poor compared to most other alternatives, but works well on metal at removing rust. At work we had a 200 litre tank of molasses which always had old car parts in it soaking - very cost effective with no need to use any elbow grease but not a goer for wood.

Metho is cheap but weak and evaporates really fast, a good thinner will usually work a lot better better if you do a comparison test. It may be dearer but it goes a lot further. As far as the acetone /thinner danger goes metho is also just as inflammable. Acetone,what woman use to remove nail polish is sold to do so because it is really aggressive compared to metho or thinner.

Don't forget also that wax of one sort or another may have been applied to a clear finish after coating maybe for many years or not at all so the effort needed to remove the finish with any product will vary every time and the older it is the harder it is. If someone has been at the finish like MacS has observed then the N/C could also have on it acrylic or shellac or some other finish how can you tell? One thing that stuffs up finishes is silicon, if you decide to do the dodgy method ond add silicon to your new finsh to stop the silicon fish eyes you make the finish entirely differnt and the new person to strike the finish wil lhave night mares removing or working on it.

Jeffhigh,
mixing the metho 50/50 with the thinner weakens the strength of the yhinner allowing you to work on the lacquer in a manner as used in french polishing it softens the laquer enough to allow you to move any peel into any low areas in the grain.

I started this and was called away and I see there has been a couple of extra comments.

pre cat lacquer is virtually the same as the old N/C its more of a name change that a difderent product, I can see any difference to the N/C lacquers of the 50/60's at all.

Acrylic lacquer is an entilely different product, grat for outside use but is a poorer finish than N/C in some ways. For instance it softens easily in slovent even petrol which N/C won't it soffens in heat and it takes months to dry as hard ans N/C. The thinner is a lot stronger and N/C thinner and attacks tiber more and is harder to use as a timber finish thats one of the reasons N/C still survives for timber finishes.

[echnidna]

Astrid, are you stripping the later art deco furniture made predominantly with blackwood veneer

[astrid]

Thanks durwood for the huge effort.
This explains a lot especialy the bit about enamals it turns into a watery gell.
I just assumed that all of the cheaper catalogue decco stuff was the same NCL.
I also think that when it goes chalky white, there probably a sealer under it because this usually happens on timber that needs a lot of filling like blackbean and cedar.
I used acetone to strip a cabinate once and although was wearing a chemical mask we were all as silly as wheels in about half an hour.
it does work a lot faster but my poor old brain cells wont cope with the damage

I strip and refinish a lot of decco Qld walnut and maple not seen blackwood vaneer.
I think Ill start keeping a record of the period of the pieces, the timber used and how they strip and see if i can cone up with a rough guide.

Thanks for all your imput

Astrid

[ubeaut]

Astrid - This was originally done as the first answer to your post but a power-out shut down the computer just as I was about to hit the Enter button. Just discovered to my surprise that Firefox saved my last session before the power-out. So here it is exactly as it was at 1:20am this morning. Apologies if I have gone over anything that others have said.

_________________________________

Astrid - Not everything you may think is Nitro actually is.

During that time there was as much furniture finished with oil varnish, spirit varnish, shellac, and a myriad of oil mixtures, as there was with nitro. Matter of fact there was probably more. Not only that but the finishes were then often refinished later on with oils and waxes and yes even poly.

That's why there's so many different effects when stripping. What you think is one finish, might be as many as 20 or more different types of finish.

Best way to strip anything is with a really good paint stripper. Lay it on thick then cover it with foil or glad wrap (I prefer foil) to keep the air from getting to it. Leave it for 10 - 15 minutes or more if needed then attack it with a scraper.

For turned or carved sections do the same initially then rather than use a scraper, use almost boiling water which has had some velvet or other good washing soap dissolver in it. Then attack it with a scrubbing brush. In most instances it will hiss and roar almost violently then the lacquer etc will literally fall off.

Don't pussyfoot around with metho and girly, eco-friendly strippers. Get in and do the job with one hit and get it over and done with. I always finish off by washing down with steel wool and metho and lots of rags to neutralize everything.

Cheers - Neil