madhattr88 Posted October 28, 2013 Report Share Posted October 28, 2013 my latest project has been quite interesting to say the least. trying to finish this one with tru-oil. the body is a mahogany - rosewood - mahogany "sandwich" i didn't want the rosewood color to bleed and tru-oil doesn't adhere to rosewood well, so after staining the mahogany top, i used a pre-val sprayer and sprayed 2 coats of 1lb cut shellac. now the problems began. i sanded the dried shellac, before pore-filling, with 320 and sanding through the red AND other parts of the shellac. So i switched to scotch brite pad. you can see in the pic i did half the top and took a pic. Applied timbermate water based grain filler (dyed black). Picture shows it drying. Sanded the filler with 320 and sanded through in a bunch of areas, especially the edges on both the top AND the sides/back. Now these areas are discolored and much lighter than the rest. Sprayed 2 more coats of 1lb cut shellac to seal everything. Look what happened on the edges. After 5 thin coats of tru-oil, this is what i got. The edges look much different then the rest. (sigh) Normally I have someone finish my bodies in nitro lacquer, but since this guitar is a gift, i didn't have the extra cash laying around. I wanted to have it done for Thanksgiving, so I can't start over. But, can anyone tell me what I did wrong??? or right? i'm willing to bet i sanded to much. I would much rather do the tru-oil sand/slurry method for filler next time, but again, worried about sanding through the shellac seal coat and colored top. How would you guys have done this????? Quote Link to comment Share on other sites More sharing options...
Ripthorn Posted October 28, 2013 Report Share Posted October 28, 2013 After having sand-through problems on a couple of builds, I switched to sanding sealer/finish starting at 1000. Sure drips and runs take longer, but I have had significantly less sand-through. I bought a box of 50 sheets of 1000 and it should last me a very long time, as I tend to use about 1 per guitar is all. I also don't sand roundovers/small bevels until I get to about 1500 or 2000 grit, as you really don't need to take much material from those parts. The last guitar turned out much better with only one tiny spot of sandthrough where there was a drip. I was able to touch it up and is now all but invisible. Hoping the next one will have 0 total sand-through. Quote Link to comment Share on other sites More sharing options...
pan_kara Posted October 28, 2013 Report Share Posted October 28, 2013 This is not an answer to any of the questions, but a stupid question of my own: does it make sense to put tru-oil over shellac? I though oil is supposed to soak into the wood ... or is tru-oil unlike e.g. danish oil in that respect? Quote Link to comment Share on other sites More sharing options...
madhattr88 Posted October 28, 2013 Author Report Share Posted October 28, 2013 This is not an answer to any of the questions, but a stupid question of my own: does it make sense to put tru-oil over shellac? I though oil is supposed to soak into the wood ... or is tru-oil unlike e.g. danish oil in that respect? it works fine. the only reason i use shellac is to seal the rosewood. trust me, i've had tru-oil curing problems with rosewood before. never had one when i seal with shellac. tru-oil is not like danish oil. it builds nicely if you put it on thin. but next time i may skip the timbermate grain fill and put on a heavy coat of tru-oil, then sand with it to make a slurry to fill the pores. just worried about sanding through again. I will also start sanding with 1000 grit as Ripthorn suggested. Quote Link to comment Share on other sites More sharing options...
madhattr88 Posted October 28, 2013 Author Report Share Posted October 28, 2013 After having sand-through problems on a couple of builds, I switched to sanding sealer/finish starting at 1000. Sure drips and runs take longer, but I have had significantly less sand-through. I bought a box of 50 sheets of 1000 and it should last me a very long time, as I tend to use about 1 per guitar is all. I also don't sand roundovers/small bevels until I get to about 1500 or 2000 grit, as you really don't need to take much material from those parts. The last guitar turned out much better with only one tiny spot of sandthrough where there was a drip. I was able to touch it up and is now all but invisible. Hoping the next one will have 0 total sand-through. Sounds good. Can you go into more detail? Do u use shellac as a sealer? what pound cut? are you finishing with tru-oil? grain filler? thanks!!! Quote Link to comment Share on other sites More sharing options...
killemall8 Posted October 28, 2013 Report Share Posted October 28, 2013 The grain filler isnt your problem at all. You can still use that. If you sand through anywhere on any type of finish, it is always going to be lighter colored, and will never match again unless you strip it. I have had that happen many times. Only way around that is to apply more finish in the areas that be prone to sand throughs. Quote Link to comment Share on other sites More sharing options...
pan_kara Posted October 28, 2013 Report Share Posted October 28, 2013 This is not an answer to any of the questions, but a stupid question of my own: does it make sense to put tru-oil over shellac? I though oil is supposed to soak into the wood ... or is tru-oil unlike e.g. danish oil in that respect? it works fine. the only reason i use shellac is to seal the rosewood. trust me, i've had tru-oil curing problems with rosewood before. never had one when i seal with shellac. tru-oil is not like danish oil. it builds nicely if you put it on thin. but next time i may skip the timbermate grain fill and put on a heavy coat of tru-oil, then sand with it to make a slurry to fill the pores. just worried about sanding through again. I will also start sanding with 1000 grit as Ripthorn suggested. thanks. good to know. I might be needing this information soon. As for the sand-through problems. I'm by no means an expert but I'd expect finishes where the subsequent coats dissolve into previous coats (nitro, shellac) to be "repairable" in the cases of sanding through by shooting more finish into the affected spot. I think I was able to do this myself with nitro once. But. This works if you have ONLY one layer/type of finish. If you have shellac over stain then sanding through the shellac you also mess up the stain underneath and that is in practice impossible to repair locally. So you basically have to strip everything and restart... Quote Link to comment Share on other sites More sharing options...
ScottR Posted October 28, 2013 Report Share Posted October 28, 2013 I would grain fill first, sand that back level, stain the mahagany, shellac, tru-oil. You can also slurry fill with shellac like you do with tru-oil. SR Quote Link to comment Share on other sites More sharing options...
Prostheta Posted October 29, 2013 Report Share Posted October 29, 2013 Slurry filling with shellac is far more difficult without pumice and alcohol that it is with Tru-oil. Shellac sets up too quickly (solvent evaporation) to keep a nice useful wet slurry for any period of time. Quote Link to comment Share on other sites More sharing options...
madhattr88 Posted October 29, 2013 Author Report Share Posted October 29, 2013 The grain filler isnt your problem at all. You can still use that. If you sand through anywhere on any type of finish, it is always going to be lighter colored, and will never match again unless you strip it. I have had that happen many times. Only way around that is to apply more finish in the areas that be prone to sand throughs. Do you think i am sanding in stages where i shouldn't be? Like after the shellac seal coats? Although it is rough after it dries. Is there any way to avoid sanding the filler. Maybe wipe the excess off the surface with a damp rag or burlap with a "spritz" of water? Quote Link to comment Share on other sites More sharing options...
ScottR Posted October 29, 2013 Report Share Posted October 29, 2013 Slurry filling with shellac is far more difficult without pumice and alcohol that it is with Tru-oil. Shellac sets up too quickly (solvent evaporation) to keep a nice useful wet slurry for any period of time. True enough. I didn't use pumice, but had to constantly recharge with alcohol and fresh shellac. It was more along the lines of a french polish without the oil or a hybrid of the two methods. It does set up fast. Is there any way to avoid sanding the filler. Maybe wipe the excess off the surface with a damp rag or burlap with a "spritz" of water? I have heard of using a scraper or steel wool. You'd probably have to watch for it being pulled back out of the pores..... SR Quote Link to comment Share on other sites More sharing options...
Prostheta Posted October 29, 2013 Report Share Posted October 29, 2013 I'm going to include basic French polishing techniques such as pumice filling in a future article. I mean to do that sooner rather than later. I bet you find it fun too, right? I'm really enjoying it. Quote Link to comment Share on other sites More sharing options...
ScottR Posted October 29, 2013 Report Share Posted October 29, 2013 I'm going to include basic French polishing techniques such as pumice filling in a future article. I mean to do that sooner rather than later. I bet you find it fun too, right? I'm really enjoying it. I didn't take it far enough to decide if it was fun, honestly. Once I got the pores filled, I moved on to spraying nitro. I do intend to read your article and then test the process out on a nice piece of scrap that I cannot bring myself to throw away. Anyone else guilty of that? Saving scraps of exotics, because they are pretty and expensive..........and mostly useless because, well, that's what scrap means. SR Quote Link to comment Share on other sites More sharing options...
Prostheta Posted October 29, 2013 Report Share Posted October 29, 2013 Not as much as I would like but still probably more than I should.... Quote Link to comment Share on other sites More sharing options...
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