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| Blotchiness on WRC Top http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=23392 |
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| Author: | Peter J [ Tue Aug 11, 2009 3:27 pm ] |
| Post subject: | Blotchiness on WRC Top |
One of my current builds has a WRC top... nice zoot from Uncle Bob. The back & sides are complete with FP and then I started on the top. After a wash coat of blonde shellac and first session of FP it really started to look blotchy. I scraped and sanded it back down and tried again but to no avail..... still has areas of lighter/darker finish and won't be acceptable to the customer I'm sure. I'm reluctant to sand it back for fear of really thinning the top. I seldom build with a cedar top and this one has me gunshy. Any suggestions to help save this one?? |
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| Author: | Bill Hodge [ Tue Aug 11, 2009 4:26 pm ] |
| Post subject: | Re: Blotchiness on WRC Top |
Howdy Peter, Unless you really have the WRC way thin it would behoove you to scrape or sand back to the bare wood and use a sanding sealer on it. Blotchiness is typical in most softwoods and some hardwoods when using any kind of tint or colorized finish. I've heard a wash coat with extremely watered down white glue will also work though I've always opted for the retail versions of the sealer. Maybe someone else has had experience with an alternate method but this is the method I am most familiar with as a professional woodworking craftsman. I hope it all works out for you! |
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| Author: | TonyKarol [ Tue Aug 11, 2009 4:50 pm ] |
| Post subject: | Re: Blotchiness on WRC Top |
I have had tops that didnt like a quick wash coat of FP as well, (some cedar, sometimes spruce, there is no way to tell until you start to do the wash coat) which is what I like to use as a sealer on tops only ... I had to just go straight to spraying the lacquer and it was better ... |
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| Author: | LuthierSupplier [ Tue Aug 11, 2009 7:52 pm ] |
| Post subject: | Re: Blotchiness on WRC Top |
Peter, I always have a blotchy look after the first coat of FP. It isn't until I get about 2 or 3 sessions where the blotchiness goes away. You may want to try brushing on a 2lb cut for the first few coats and see if the blotchiness goes away. |
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| Author: | Dave Livermore [ Tue Aug 11, 2009 9:47 pm ] |
| Post subject: | Re: Blotchiness on WRC Top |
I've had the blotchy look and discovered that it was due to the oil I used as a lubricant leaching through the seal coat into the wood in places. Once the oil gets through, it is REALLY tough to get it out of that spot or spots completely. I've see a pro finisher do an FP by beginning the session with a coat of oil across the entire surface and then begin building up the shellac. He just dumped lemon oil on the board, let it soak in a little and then started applying shellac. I was pretty freaked by it, but the result he acheived in a few minutes was amazing! If this was the problem, try something on a test board by first putting a few spots of oil on it. Then start the FP. See if you have blotches where the oil was. If so, scrape back, put a light coat of oil on it and then start the FP again. Observe if it is uniform. This is merely a suggestion and I realize there are many ways to fix the problem, avoid the problem and hide it. Maybe it will work for you, maybe it won't. The test piece will at least give you a buffer before you do anything to remedy or make the problem worse. good luck. Dave |
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