Omar Al-Mufti
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Stripping polyurethane finish
Dear forum members,
Any idea how to strip polyurethane lacquer from an oud back?
I read about some water basis strippers which are claimed to remove that lacquer easily leaving the wood undamaged
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Brian Prunka
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What is often called "polyurethane" can be any of a variety of synthetic finishes, commonly including polyester.
If it really is polyurethane, a chemical stripper that says it can remove polyurethane or acrylic finishes should work. be careful of any chemicals
(gloves, ventilation, and some kind of respiratory and eye protection are recommended) and do a small amount at a time. You don't want to get the
wood soaking wet. A plastic putty knife with the edges sanded off helps scrape it off after the stripper has softened it.
Unknown synthetic finishes are often stripped with a heat gun, but this is definitely not a good idea for ouds.
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Omar Al-Mufti
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Many thanks Brian.
Do those removers have any negative effect on the wood?
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Brian Prunka
Oud Junkie
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That is a tricky question. You are not asking about either a known finish or a known solvent, so there are a lot of unknown variables here. You don't
mention the kind of wood, either.
Typically things do not penetrate the wood deeply and one will typically do some sanding/scraping to prep the wood for a new finish, so as long as the
wood doesn't get wet enough to warp or for joints to fail then it will probably be fine. But one should be very careful, as wood and glue are
sensitive to moisture and ouds are of particularly fragile construction. That's why I said do a small amount at a time. There will be some surface
effects, such as raising the wood grain. If there were dyes used in the wood or the finish then these may be affected. Like almost anything
involving ouds, you can cause damage if you are not careful. If the stripper is made for wood, though, it is basically safe to use on wood. But of
course, an oud is more than wood. Be very careful around any inlay or binding/purfling, as these may be plastics, which can react unpredictably to
mystery solvents.
The totally safe approach is to sand the finish off. Which is a lot of work and almost certainly not worth the trouble. I am curious what oud has a
synthetic finish that you are interested in going to all this effort to remove.
No doubt there will be further suggestions from some of the expert luthiers here, most likely advocating extreme caution and taking it to a
professional. I've stripped a few instruments but have stayed away from anything heavier than lacquer due to the greater risks and complexity.
Lacquer and shellac are relatively easy and simple.
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jdowning
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How do you know it is a polyurethane lacquer (varnish?) - rather than, say, an 'old fashioned', non synthetic, linseed oil based varnish finish
traditionally used by - for example - violin makers? Just curious.
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Omar Al-Mufti
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Jdowning, because I know the maker 😊
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Omar Al-Mufti
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Brian,
Thanks again..I appreciate it.
Actually the oud worth it.......and the oud maker is one of the finest......but I H A T E synthetic finishes. ....
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jdowning
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?!
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Omar Al-Mufti
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Jdowning...I meant I am sure of the type of lacquer because the maker told me....plus it looks typically
poly finish
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Brian Prunka
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The maker may have an idea what stripper would work . . .at least ask him the exact manufacturer and product, then you can research it
specifically.
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Omar Al-Mufti
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Brian, I would follow your advice. I would do small areas each time, so that I guarantee no mess could happen, and no structural damages could happen.
By the time one area is stripped, dry and settled, I could start with the next.
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Brian Prunka
Oud Junkie
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I'll add that based on my experience, strippers tend to have a certain window of maximum effectiveness . . . it may take a little trial and error to
find where that is.
For example, you may find that until 9 minutes the finish is still too hard and takes a lot of work to remove, but from 9-15 minutes it becomes very
easy to remove, and after 15 minutes it becomes difficult again to remove.
The timing and duration of that window will vary based on the particular finish and the kind of stripper being used. If you can time it just right,
it becomes much easier and with less stress on the wood (if you time it perfectly, you just have the stripper penetrating the finish, softening it,
and not touching the wood at all). The main reason to start with small areas is to figure out when that window is, and to make sure you have enough
time during that window to remove all of the finish/stripper so you don't have to reapply stripper to the same section.
I've only stripped shellac and lacquer, so I don't know what your working time will be like.
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