Are there any chemicals to help strip Minwax Spar from a pine pic table?

[bent]

Is there a good chemical for helping to remove a few layers of Minwax Helmsman Spar Urethane clear Satin finish that may be one to several years old. For my 20 year old summer pine picnic table. Every other year or so I scape and sand, sometimes to bare wood on a great portion, but its always a hassle, iirc the book Understand by Flexner talks about a chemical for removal of finish like this this and I think the main chemical component is MEK (methyl ethyl ketone), but I forget the details. I believe it was said to be unobtainable, but I do think I have seen some form of this chemical component in a variety of things, like pvc or abs glue for a guess, and I have always thought of finding out if there is some way to get me a good stripper for this job one day. Ok, I checked, the "Oatey ABS Cement" says "Contains Methyl ethyl ketone", and the "Oatey PVC Cement" says "Contains Methyl ethyl ketone, Tetrahydrofuran, PVC Resin, Cyclohexanone. I have never tried either of these, and don't know what would happen. I have tried but anything chemical I have ever tried has always fallen short of being advantageous, sort of dissolves but can't cut it. So for the dozenth time I have a cabinet scaper (still can't sharpn it yet), paint scraper, putty knife, sand paper (by hand and 1/3 sheet vibration m/c). I have learned over the years that the liquid chlorine (~$10/ 50L from the pool store) does a good job of bleaching white any of the bare wood that has darkened, possibly due to water. But its the same old time-consuming labour grind for the poly prep re&re. I ask now because all and every of the ~75 sq. ft. of pine pieces are 100% apart, and I have a chance to make it right between the cracks this the first year ever. So, any hopes of actually finding some help with the removal via a chemical.

[nailshooter41]

[Lew Hodgett]

Your basic paint remover is basically Sodium Hydroxide (Noah) AKA: "Caustic", with an inert carrier.

It should be neutralized when finished with acid, usually phosphoric, and finally water..

If you not careful, caustic will soften the pulpy part of the wood being cleaned. Don't leave on and forget about it.

I'd start with so 60 grit to cut thru the dirt and the bulk of the varnish, then use NaOH.

The commercial paint removers will have a carrier to hold them in place.

Apply with a chip brush.

BTW, SFWIW, acetone is probably the most powerful of all the keytones.

Lew

[J. Clarke]

Have you tried purpose-made paint stripper? Any paint store, home center, or decent sized hardware store should have it in several varieties. Get the smallest size they have, try it on a small area, if it works then get enough for the whole job, if it doesn't work then try a different brand until you find one that does. The trick is to get it on thick enough and don't let it dry unless the label specifically says that you should.

Read the label, follow all precautions, make sure you have the right gloves and a set of chemical goggles--some paint strippers can give you a nasty burn if you let them.

While I'm sure that there are MEK based strippers out there the most common chemical used is methylene chloride.

[ransley]

[Scott Lurndal]

[Lew Hodgett]

Chalk it up to the spell checker, it nwas late and it got me

Lew

[nailshooter41]

I have a commercially available stripper that is favored by the aircraft industry to strip mutiple coats of Imron and other high performance coatings.

It is a deadly concoction of Sodium Hydroxide, MEK, Acetone, some kind of Benzine, Alcohol, and other goodies. It is the nastiest stuff I have used to date, available to commercial accounts only. It will actually eat into lower quality latex gloves.

I was using it to strip a door that had a couple of coats of spar, then a couple of coats of poly on top of that. It ate through in one coat of stripper in a lot of places!

I brushed against the door when I was coating it and got that stuff on myself. I felt it burn a bit, but thought "as soon as I coat this side and cover, I'll rinse it off". Fifteen minutes later I had a burn on my arm that was surprisingly bad, and I couldn't get it to stop burning. A couple of days later the skin fell off, and I still have a scar today to remind me to be more careful.

On the other hand, I have tried the soy based stuff, the fruit acid based stuff, and anything else I could try, and nothing works nearly as well as the highly toxic, flammable, poisonous fumed, environmentally dangerous stuff.

Go figure.

But I will say this - if I only have 2 - 3 coat of finish to remove I use the Bix. The other stuff scares me.

Robert

[Lew Hodgett]

"Benzene" is enough to get the stuff restricted.

Way back when, Rochester Products offered a carb cleaner to clean up a gummed up carb.

Remove the air cleaner and pour it right down the carb while running at a fast idle.

Did a great job cleaning carbs, but oh the effects on the environment.

Lew

[Baron]

I appears that you are over analyzing the project. It is really much more simple than you might think.

1) Clean the table. First, brush off all the loose dirt. Then, use warm, not hot, water containing Dawn dishwashing liquid, one capful per gallon. I like Dawn since it has a neutral pH but any dishwashing liquid will work. Don't saturate the table, use just enough to do the job with clean rags. Rinse off with fresh water. Again, do not saturate the table. Wipe down to dry. Now, go over the table with odorless mineral spirits. Use lots of clean rags. You can saturate the table if you like but it really isn't necessary. Allow to dry. The purpose of this step is to get the dirt off the surface that can interfere with penetration of the finish stripper. 2) Apply a good finish stripper. You do not need a caustic stripper. Find a paste one that has methylene chloride. This is a fast and strong stripper. Other strippers will either work very slowly or are so corrosive / caustic that you might actually damage the wood. Read the ingredients so you can pick the right one. A very rough rule of thumb is to use the heaviest one you can find. Methylene chloride is denser than any of the other organic solvents that are used in finish strippers. It is even more dense than water. It is also more dense than the waxes used in the paste strippers. The heaviest can, assuming equal volumes, will probably contain the most methylene chloride. Apply the stripper with a brush or rag and don't be stingy with it. 3) After allowing the stripper to sit as per the instructions on the can, scrape it off. You can use a plastic or metal tool. I like plastic since it is less likely to accidentally gouge the wood. 4) Without any wiping, apply a second coating of stripper. Let it do its thing and scrape it off again. 5) Go over the piece with #1 or #2 steel wool or the equivalent ScotchBrite pad. Saturate the wool or pad with stripper to do this. The idea is to remove the last traces of finish without scratching the wood to any great degree. You should go over the whole piece to make sure it is evenly rubbed. 6) Wipe down the piece with lots of clean rags and then with mineral spirits to remove any residual wax. I like to use a 1/1/2 (v/v/v) solution of alcohol / acetone / toluene. This not only removes the wax but it keeps any residual finish from readhering (sp?) to the piece. 7) Admire your work.

Remember to pay attention to all the safety warnings - lots of ventilation, no open flames, use gloves, eye protection, etc.

Good luck.

[bent]

NOTHING CUTS IT Well I've done some scraping (claw scaper best) and sanding, and have tried a few chemicals that are next to worthless. They sit on the surface, bubble a bit, then when wiped off it just looks like a cleaning. They will just melt a very thin top layer, but cannot cut down to the wood, kinda like a spilled tequila. I am serious. Maybe after thirty coats (liters). I tried the Oatey (with MEK) and $5 for 250mLLepage Poly Super Strippa extra strength (with methylene chloride). Ive got half a dozen things with methyl alcohol and the like, but its not even worth opening the bottle. Total complete joke waste of time, as ever. Its much better to attack with tools or sandpaper, no matter how affixed. Lots of labour and only half done. So at least it wont be coming off anytime soon. So I say again to anyone who needs to do this, good luck, youre going to need it.

FLUSHING THE CHLORINE (WONT STICK) Next pertinent ngQuestion. Like I said, especially where there has been water exposure (you know what black wood looks like). I have concentrated liquid chlorine from a pool, and lots of it, cheap. It bleaches that black to a very bright white-like. But in the past after the few times when I have done this the poly does not want to stick to it very well. It literally just flakes (falls) off not long after. So can anyone recommend a procedure, or series or neutralizing chemicals, or soaps or anything please do. I have tried a blast of water and drying, but its just flakey. I am open to any suggestions, however primitive. I have not done this chlorine bleach test enough to remember how much water and how fast it turns black, so that the flush doesnèt ruin the bleaching effect, but again, after 25 years on this table its a black and white, with a little gray area. This chlorine, which is stored indoors at pool stores in 6 foot Dia. by 12 foot high plastic silo containers, if splashed on jeans (or anything) will turn that spot white, threadbare like silk within a day, and soon be nothing but a round hole.

What I did learn this year is that one of the 2x12x8 pine boards got rain & snow soaked all through the winter and is water logged, and it strips much more completely and easily than the dry boards. I know now how to make it bright agian, but now I need to learn or experiment on how to make it hold a finish after that treatment. Ideas, anybody: a little chemistry for a dummy.

[Steve]

"bent" wrote in news:1214063894 [e-mail]:

That's pretty much the way strippers work. They all brag about removing

23 layers of paint at once, but I've never seen it in real life. I've also noticed that they work better on paint than on varnish/lacquer/polyurethane.

If the stripper dries out before you scrape, you've wasted your time. You might try putting on a really thick coat of a gel-type stripper, then covering it with something like aluminum foil to keep it from evaporating. That will allow the solvents to work longer.

I've had the best luck with those that contain methlyene chloride.

[Steve]

"bent" wrote in news:1214063894 [e-mail]:

The chlorine oxidizes the mildew to remove the black stain; it also oxidizes the wood, leaving a surface layer that's probably similar to ashes (that's also oxidized wood). I would sand the surface after bleaching it.

[Norminn]

I've used Strypeeze (meth. chl.) and never had difficulty removing old finish. It has to be used properly - thick, not brushed out, away from direct sunlight and breeze. It takes varnish off more quickly than it does paint. Use a scraper to remove the softened gunk and apply again.

20-30 min. generally is fine. After last scraping, I usually apply stripper again, scrub with steel wool, scrape that off and end by scrubbing with steel wool and mineral spirits. Wife off last of that and let it dry.

I've read that the black stain in wood is from iron compounds oxidizing. Also read a tip about using rust remover to remove this type of stain, but have never tried it.

[Norminn]

In my experience, varnish loosens more quickly but tends to remain in a "sheet" more than paint. When I am doing a large project of removing paint, I scrape off the mess from the first application, into a coffee can, and reuse it on another area. It is ugly and messy, but doesn't seem to loose strength.

Methylene chloride semi-paste is the only way to go, IMO. If not applied thickly, it will dry before it loosens the finish. There is nothing in the way of finishes that I have found that will not be taken off if used properly.

[Lew Hodgett]

BET ME.

I have a belt sander with 24 grit belts and a 6" ROS with 40 grit discs for clean up that will get to bare word in a hurry.

Lew

[Baron]

To remove black stains on wood due to water exposure, try oxalic acid. You can get this as deck brightener. Just look at the ingredients to be sure. Assuming the black stains are not due to mold, they are due to the reaction between the tannins in the wood and iron. Oxalic acid destroys the complex so the black disappears.

As for the finish strippers not working perfectly the first time, you have to keep at it. The bubbling suggests that they are working. No one ever said, expect perhaps for the stripper salespeople, that stripping a finish is easy and quick.

Good Luck.

[bent]

Its tempting to try my sander but I don't know if I'll need to measure the job by the sheet or by the machine. I have all 6 edges and another 30% of the ten boards faces cleared so far, with a Richard paint scraper - great tool, just keep sharpening with a file.

[bent]

Make that all four edges (of all five boards) plus 22 of 72 total sq. ft. cleared. So 50 sq. ft of face(s) left, in patches. Usually I'd just start poly but I now have decades of dirty edges cleaned up and soon to be brightened .

[bent]

I also have this 4-1/2" angle grinder, and the rubber pad accessory and a half dozen round sandpaper disks. Anyone think this might be worth a try?