Stripping Polyurethane

[chopnhack]

Has anyone used this product yet?

I am contemplating refinishing the front doors. The poly has long given up the ghost... south facing doors in florida, yeah, they never had a chance! We noticed the finish starting to get crappy a few years ago, but at this point it is lifting and blistering in the concave areas of the molding. I didn't want to refinish with poly again because of the short lifespan.

What do you use for stripping? It was minwax polyurethane, not WB over brazilian oak? What would you suggest for a finish? I was thinking of trying the red label penofin.

[jdon]

I recall reading that methylene chloride based stripper will work on polyurethane (gentler formulations don't work), but have no first hand experience

[herb fellows]

I have done several doors with methylene chloride stripper, it works very well, but with these caveats:

It is nasty stuff, protect your skin thoroughly! It will begin to burn you in about 5 seconds. You also need to use it in a 'well ventilated area', as they say. Personally I only used it outdoors as the smell alone would permeate the house for days afterward.

When it pulls up the poly, which it will do in about 2 minutes, it creates a muddy mess when you go to clean it up.
You need to do quite a bit of end game stuff with rags, thinner etc to have it come off completely. I would suggest doing very small sections at a time, no more than maybe a square foot if possible.
However, don't let it sit on one half of some part or do half of a part at a time, it will leave a mark where you start the new removal which even sanding doesn't remove.
The stuff I used was Klean Strip ks-3, a paste.

[cabinetman]

Has anyone used this product yet?

I am contemplating refinishing the front doors. The poly has long given up the ghost... south facing doors in florida, yeah, they never had a chance! We noticed the finish starting to get crappy a few years ago, but at this point it is lifting and blistering in the concave areas of the molding. I didn't want to refinish with poly again because of the short lifespan.

What do you use for stripping? It was minwax polyurethane, not WB over brazilian oak? What would you suggest for a finish? I was thinking of trying the red label penofin.

Forget about that Rustoleum product. It won't strip polyurethane. I would suggest using the sweat off my brow, but, I'm not there to help you. It must be toxic as I've done some serious damage with it. Maybe that's why the Army put me on the front lines.

Herb had some very good suggestions. MC based strippers are extremely toxic. I would recommend using gauntlet type chemically resistant gloves, face/eye protection, and a good two cartridge respirator. Even with all that, work in a well ventilated area.

The best over-the-counter stripper I've used is "Aircraft Stripper" in the blue can. If you can't find it in the box stores, automotive supply stores or dedicated auto paint and supply stores will have it.

I've done my share of exterior finishes using top grade marine finishes, such as from Interlux and Epiphanes. All film finishes will fail, and when they do (which is usually sooner than later), they get that crispy look. What a PITA to maintain. A lot of work, including more sanding than you can imagine. With exterior doors, unless you can hang a temporary door while you are refinishing, you will be working at some weird angles.

After my last adventure with a Mahogany door that I made, I finished with a marine spar, and didn't get a year out of it. Since then, I use Penofin Red Label. All I can say is that it's an easy finish to use and maintain. It has a high UV factor. Any finish will need some maintenance, but with Penofin, just clean the door, and re-apply. It comes in a variety of colors and clear. Try it on a sample to see if you like it.

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[chopnhack]

Thanks all, I was trying to avoid anything toxic as the one of the wee ones gets respiratory stuff too easily.

If I got to do the MC based stripper, I will, I like the fact that its quick, because I need to have the doors back up in operation asap, I don't want to have to build a temp. door.

Herb - Can you elaborate on this a little, I like the info, but it left me confused: << I would suggest doing very small sections at a time, no more than maybe a square foot if possible.
However, don't let it sit on one half of some part or do half of a part at a time, it will leave a mark where you start the new removal which even sanding doesn't remove.>>

You said to work in small sections at a time, which I like, but by working on small sections at a time you are effectively leaving it on a part at a time?

Please clarify for me further, I sorta understand what you mean but its not clear. Thanks!

Cman, this is what I have found down here as well, film fails quick and its not pretty. What colors have you worked with in the red label? Care to comment on the hues?

After stripping the poly, I intend to sand lightly, should I use 220 or greater? I don't want to affect the underlying stain. I still haven't learned how to match old work

Will the stripper remove the old stain?

[wardprobst]

Have you tried a heat gun? Another alternative is one NMP strippers that flash off really slowly but it sounds like it's going to be messy. Finally, I know you don't want to do a temp door but if you did you could take them to someone with a flow over system and be done with the stripping pretty quickly.

Hope this helps,
DP

[chopnhack]

Thanks DP :-) These are south facing doors in florida, I figure they already had the heat gun on 'em But, no I haven't tried that. The poly coat was exceptionally thin - pretty sure it was a one coat job since they were late installing the doors, but they lasted since about -'05 Yes, I know I probably should have refinished them about 2-3 years ago, but I put it off since its such a hassle with children around.

Not sure about the flow over system.. I really don't know where I would find one, but the door has leaded glass inserts so I don't want to dunk the door. The inside of the door's finish is in awesome shape, so I will only be stripping the outer face.

I have been thinking about picking up a roll of frog tape to seal off the edges as I really only want the exposed face of the door to be stripped. I never used it before, but I remember my buddy at the paint supply telling me about this stuff when it first came out. He said that the edge gets wet and seals itself off - I figure I can run a wet finger over the taped edge before I strip.

Anybody use this tape before?

[herb fellows]

Thanks all, I was trying to avoid anything toxic as the one of the wee ones gets respiratory stuff too easily.

If I got to do the MC based stripper, I will, I like the fact that its quick, because I need to have the doors back up in operation asap, I don't want to have to build a temp. door.

Herb - Can you elaborate on this a little, I like the info, but it left me confused: << I would suggest doing very small sections at a time, no more than maybe a square foot if possible.
However, don't let it sit on one half of some part or do half of a part at a time, it will leave a mark where you start the new removal which even sanding doesn't remove.>>

You said to work in small sections at a time, which I like, but by working on small sections at a time you are effectively leaving it on a part at a time?

Please clarify for me further, I sorta understand what you mean but its not clear. Thanks!

Cman, this is what I have found down here as well, film fails quick and its not pretty. What colors have you worked with in the red label? Care to comment on the hues?

After stripping the poly, I intend to sand lightly, should I use 220 or greater? I don't want to affect the underlying stain. I still haven't learned how to match old work

Will the stripper remove the old stain?

I hear you, it's almost like a catch 22 situation, ****ed if you do and ****ed if you don't:-(
The key words in what I said were 'if possible', which is obviously not when doing a full sized door.If you have sections that are more than a square foot, you sort of need to do them all at once I suppose. Depending on how quick you are, you might have to re apply remover, but this is the lesser of two evils, as the stain left when you stop in the middle is virtually impossible to remove.
Much as in painting, you need to keep a 'wet edge'.
The bottom line is not to leave a mark where you ended one section and began another.
This stuff is supposed to skin over when exposed to air so that the remover underneath the skin keeps removing, but I've found that it tends to lose its potency after 5 minutes or so, ymmv.
Two other things: I find it works better when you remove with the grain, so if there are any loose bits they are less likely to tear out.
To clean up the final muck before 'washing' it with thinner, I use a razor blade at about a 25 degree angle to sort of corral the last bits of the film and sop them up with paper towels or whatever.
You do have to constantly clean your tools as the muck/remover mixture hardens on them. I keep a coffee can with remover in it next to where I am working and after removing the bulk of the muck from the scraper I soak it in there for 10-20 seconds to make it easier to remove the rest from the tool.
I started out using steel wool to clean the tools until I realized I would need about $400 worth to complete a single door! This stuff just mucks up everything! Have tons of paper towels handy, you'll need them.
So obviously good to work with 2 scrapers if you can.
No matter how you look at it, it is a messy, slow process, but if you keep on point the results are well worth it.
That being said, maybe the aircraft stripper c man uses functions a bit differently in some of these aspects, i can only vouch for the product I've used.
Best of luck!

[cabinetman]

Here's a suggestion that you might try FIRST. Many oil base varnishes and polyurethanes can be stripped using a waterbased gel stripper like Citrastrip.

It's no where near the toxic levels of an MC based stripper. It can be used indoors, and smells like oranges. It's gel state doesn't run, which is helpful if working vertically. You may need to use more than one application, but if it works it may be a lifesaver. Try a small container and see what it will do. That's what I would do first. Then if it has no effect, go to an MC based stripper.

I just got to thinking of the times I stripped existing exterior doors and the absolute mess it makes. The cleanup would be much easier too, as the final wash up would be done with water instead of a solvent.

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[chopnhack]

Thanks guys, really appreciate your input and experiences. I will be removing the doors amd putting them on horses to work on, but the citrastrip sounds worthwhile

[wardprobst]

Okay, I have a better idea of what you are up against. I would try a heat gun with the door in place; we know it will work because the Florida sun has been working it already. If it was in my part of Texas, you'd be sweeping it up.
The only problem with the slow strippers like citrus, soy and NMP is the amount of time they take to work. Also, it sounds like you want to save the inside finish and that could be problematic as stripper tends to go where you don't want it to go. I would give heat and a brush or putty knife a try first just to see if it will work. It's way less messy. You can always to to stripper if it doesn't work.

DP

[chopnhack]

DP, also a valid point DP! Thanks. That cheapo HF heat gun has been on my list for some time, maybe I have an excuse to pick one up now

Have you used a heat gun to strip poly before? I am curious as to how effective it will be.

Cman - on the Penofin, have you used the transparent or colors?

[cabinetman]

Have you used a heat gun to strip poly before? I am curious as to how effective it will be.

You have to get it really hot, and it gets gummy. You still need to scrape it off.

Cman - on the Penofin, have you used the transparent or colors?

I've used the clear on projects that the species was an important factor. I used a transparent color on the project below.
http://bt3central.com/showthread.php...ighlight=patio

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[chopnhack]

Do you remember what color you used on the table? It looks like it greyed/tanned out in color.

[cabinetman]

Do you remember what color you used on the table? It looks like it greyed/tanned out in color.

I'm pretty sure I just used clear. The other color I had was mission brown. I may have added some to the mix. But, it was PT SYP to start with, and that stuff has a greenish tint and some brown running through it. I would suggest you to try a sample before you do the door.

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