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Techtchr
04-07-2004, 07:55 PM
As some of you know I repair musical instruments.I often have to strip the finish off of brass instruments. This is a long standing problem that I have not been able to resolve. King musical instruments have a very tough lacquer on them that is almost impossible to remove. Over the years I have tried all the typical paint removers and solvents. Methylene chloride has a partial effect on it but it usually takes 3-4 days before it comes off, and then the brass underneath is starting to be affected. These are some of the things I have tried over the years: Paint stripper (both the methylene chloride based and the enviro friendly stuff), alcohol, lacq thinner, paint thinner, brake fluid, oven cleaner, keytone, acetone, and boiling in washing soda. The boiling in washing soda works for small parts but I don't have a tub big enough for most things.

I've heard from some of the old time repairman that they use to strip lacquer and paint in a heated lye solution. Anbody ever do this and if so how do you do it safely and where does one get lye? Farm store?

I hate to setup Thrud like this but, do any of you have any good solutions for stripping? (paint that is)
Thanks Matt

gvasale
04-07-2004, 08:20 PM
The oven cleaner you mention may indeed be lye. It should be available in the cleaning products isle at a good supermarket. I can check some containers I have around and report back. A strong ammonia solution will break down laquered clock plates, but not immediately. Have you tried tri sodium phosphate?

Techtchr
04-07-2004, 08:31 PM
No, I haven't tried TSP. I thought it was a cleaning or degreasing agent. I'll look into it. Thanks
Matt

Evan
04-07-2004, 08:31 PM
Lye is sodium hydroxide and is available in the supermarket in the laundy detergent aisle usually. It will attack aluminum in seconds, don't know about brass but I suspect it may go after the zinc. Try a test first, of course.

Evan
04-07-2004, 08:35 PM
You also might look for graffiti and spray paint remover.

Forrest Addy
04-07-2004, 08:38 PM
Try a straight lacquer thinner in a closed sealed metal container having a sinicone rubber gaslet. If you warm it to about 120 degrees it will strip any organic coating given time and it will not harm (except to discolor slightly) brass or copper alloys.

This operation is not without flamibility hazards. Do the job out of doors. Warm the container in a double boiler arrangement.

Techtchr
04-07-2004, 08:54 PM
Thanks for the safety warnings. I do almost all my paint stripping outside. The heating part is what my problem is with the lye solution too. Although I would feel more comfortable heating the lye than trying a double boiler and lacq thinner.

The sealed container is also a problem, as things like trombone slides are about 3' long. Sousaphone branches are long and curved. Finding an economical container that won't be eaten by the chemicals and can still be heated is also an issue.
Thanks, Matt

ACF
04-08-2004, 12:38 AM
Matt,

If you know someone in the chemical industry that can get you some
N-methyl-2-pyrrolidone solvent,it would be worth giving a try. As with most things it will work better warm. Boiling point is
202 C. and flash point is 95 C. so it is a fairly safe solvent, but use in a well ventilated area.

Chris

WJHartson
04-08-2004, 01:31 AM
For a container large enough to handle the large instruments you might see if you can locate a used stainless steel 30 gallon drum with a lid. Beer kegs and some of the old milk cans are made of stainless steel. Look on the web for distillation stills and you might find other ideas for containers.

We have some large stainless pot for boiling seafood. The have lids but they don't seal.

Hope this helps.

Joe

CCWKen
04-08-2004, 01:31 AM
Ummmmmm. If Lacquer Thinner fails to remove it, it may not be lacquer. Lacquer based paints can always be reduced from a solid with solvent. That's what was so great about true lacquer paints. It could be dried in a can and you could still use it by thinning. It doesn't polymerize or crosslink like other paints.

You said you've tried the M-C based strippers but where did you get it? Most are very weak. I use Aircraft Stripper available at Autozone or auto-paint suppliers. The only time I've ever had a problem with it was on baked enamal. It works, but takes a long time (an hour) and has to be kept wet. Also, it helps to scuff the surface of the paint (This is the hardest layer). Use a grey 3M scuff pad then apply the stripper.

[This message has been edited by CCWKen (edited 04-08-2004).]

Techtchr
04-08-2004, 12:47 PM
Thanks again for all your responses. I will check the options for containers. CCW, as far as the term "Lacquer" goes, you are right. Some finishes are actual lacquer and some are epoxy finishes and still others may be something else. A "lacquered" horn in the music biz is one that has a clear finish on it. Kinda like people calling all adjustable wrenches crecent wrenches. As far as my source for M-C, we use to buy it straight from a chemical supplier in 5 gallon pails when I worked in the repair shop full time, but now that I'm doing this only part time and don't have access, I buy the M-C based stripper from the hardware with almost identical results.

Chris, what is "N-methyl-2-pyrrolidone" ? I know M-C is know to cause cancer and other ailments... how toxic is the N-methyl in laymans terms?

Evan
04-08-2004, 12:50 PM
Matt,

See here:

http://www.lyondell.com/html/products/products/NMP.shtml

Try graffiti remover.

[This message has been edited by Evan (edited 04-08-2004).]

ttok
04-08-2004, 05:28 PM
Use a methylene chloride stripper like Aircraft Stripper from Autozone, but cover the surface of the wet stripper with plastic sheet (even an old grocery store bag will work) immediately after it is applied to the part. This will retard evaporation of the volatile active ingredient and let it penetrate deep into the old paint. Give it about 15 minutes to work. You will use a lot less stripper and the paint will come off a lot easier. CAUTION: Methylene chloride causes liver cancer and burns skin like fire! Do not inhale it or leave it on your skin (too painful to do that anyway!).

ACF
04-08-2004, 05:52 PM
Matt,

Evan has posted a link to a supplier of NMP. Wear gloves so it doesn't get on skin as it will remove the fat from your skin and make it dry as hell.

Chris

Pete Burne
04-08-2004, 06:37 PM
Tech:

Don't use lye on brass. Brass is a copper/zinc alloy and zinc is amphoteric(sp?) which means it dissolves in acid AND caustic; it is commonly called dezincefication.

Well known to boat owners who cheap out for brass rather than bronze.

Pete

Samuel
04-08-2004, 06:53 PM
this might seem a bit petty but did you contact the company yet? I meen you know, they may just tell you what to use. I had a friend that went to school to repair brass somewhere back east and he said someone in his class "forgot" a trumpet in the dip overnight and when they came back the next day it was gone up the dip line. maybe a clue?

Samuel

Bruce Griffing
04-08-2004, 07:34 PM
Why not remove it mechanically? The removal would then be limited to the area you needed to remove. Cratex wheel? Hard buffing wheel with a brass polish?

Techtchr
04-09-2004, 08:44 AM
Sam, No, I haven't called them in recent years. Long ago I did and they would not release the info. Probably time to try again. Your friend probably went to the same tech school I did. There was only one in the east that I know of. Morrisville, NY. It is now long gone closed in the late 80's. I graduated in 81. Leaving a horn in M-C will not deteriorate the brass, but it leaves a layer of material on the horn that is also a PITA to remove. He probably left the horn in "brite Dip" which is chromic acid. Typical application was to leave it in a few minutes. Over night would make it disappear Opps! I use a different acid to clean out the inside of horns now, and flush with lots of water.


Bruce, mechanical stripping is kind of what I currently do. What ever is left after trying to chem. strip is buffed off. This is not a teriffic option, because if you need to remove the lacq around engraving or intricate parts, it washes out the engraving and rounds sharp edges of turnings. Chemical stripping would be much better. I wouldn't use the cratex wheels for this.

Evan, thanks for the link. I have a pretty good relationship with a local paint supplier, I'll see if he can get me a small quantity to try. Looks like it has good potential.

If anyone is interested I have a King t-bone that I bought for my daughter that I plan to repair soon.(spring break project) I will take before and after pictures. and post on photo bucket.
Thanks again to all.

Matt

Samuel
04-09-2004, 10:23 PM
um I saw that you mentioned Ketone, but I also thought that it was odd that you mentioned acetone, which is a ketone, so I thought that I would make a list and see if there was anything " obvious " that hadnt been used. also my friend went to school "recently" I think somewhere a bit more west, like Colarado, or Minnesota. but I just cant remember exactly.

this is out of a book so bare with me here

Aliphatic hydrocarbons:
n-hexane
vm&p naptha
mineral spirits
kerosene

Chlorinated Hydrocarbons:
methelene chloride

Aromatic Hydrocarbons:
Benzene
toluene
xylene

Alcohols:
ethanol
methanol
isopropanol

Ketones:
acetone
methyl ethyl ketone
methyl n-butyl ketone
methyl isobutyl ketone


others:
methyl cellusolve
diglycidyl ether

also did you try cyanoacrilite release?
and I know that there are alot more but this is what I have listed in my book thats at hand.

also, did you try poking around a shop that work on brass? or call them?
maybe its clear platinum http://bbs.homeshopmachinist.net//smile.gif

Techtchr
04-13-2004, 08:59 PM
Thanks for the list Sam. Is clear platinum related to the clear aluminum in the star trek movies?

I have tried some of the items on your list, but not all. I will check some more.

Western Iowa Tech, Renton vo-tech. Renton WA, Red wing vocational Re wing MN. Are the few schools for band instrument repair that are left.

Thanks, Matt

lunkenheimer
04-15-2004, 03:10 PM
Though it was mentioned that you shouldn't use lye on brass, I thought it might be good to know that good ol' powder drain cleaner is pretty much straight lye (Red Devil brand or Drano)

Just in case you need some to make soap or something...

J Tiers
04-15-2004, 06:50 PM
I agree no lye on brass.

But to get lye, plain purple cleaner is pretty much lye.

Example: Zep Industrial Purple cleaner/Degreaser.

Most likely the "lacquer" is no longer a real lacquer, but is a polyurethane or other similar material, for EPA and / or performance reasons. Polyurethane can be had in water-borne "eco friendly" varieties.

However, it may be much less susceptible to many strippers etc once it has finished crosslinking.

Samuel
04-15-2004, 08:48 PM
I did a google search just for fun, but also because I am confident that king doesnt brew thier own finish. I found alot of info but some of the products are similar. here is one that sounded similar to what you may haven encountered. www.por-15.com (http://www.por-15.com) also some of them have been described as solvent resistant, only soluable by some sort of chlor-meth-di something hope this helps.

Samuel

Michael Az
04-16-2004, 11:20 AM
Techtchr, too bad we are so far apart, I have a 3,000 gal stainless steel tank I'm not useing.
Michael

Forrest Addy
04-16-2004, 12:30 PM
Let's see. Closed containers for whoppin' big delicate brass instrument parts like from sousaphones and tubas.

How about a big steel drum with a gasketed lid? I'm thinking of the type drum used to double enclose damaged and leaking 55 gallon drums. I think they're 65 gallon and 37 inches deep inside measurement. A trombone slide os a sousaphone bell will surely fit inside diagonally.

Contact a shipping drum recycling company in your nearest large city.

Do not use caustics on brass. It will leach out the zinc from the metal and leave the copper sponge behind.

docsteve66
04-16-2004, 10:57 PM
Forrest: sounds as though you too had dealings with "waste" stuff.

I had charge of about 1000 55 gallon drums that leaked (paints, strippers, plating solutions). Some one found plastic drum that was (as forrest says) big enough for a 55 gallon to slide into. The plastic was inert, strong (and expensive too i bet)