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| Tru-Oil Blotchiness http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=19796 |
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| Author: | Pat Hawley [ Tue Nov 25, 2008 9:48 pm ] |
| Post subject: | Tru-Oil Blotchiness |
I've just done my first coat of Tru-oil on my present guitar. There are some spots on the neck where it went on kind of blotchy. Especially on heel and on the volute where there are spots that look lighter than the rest of the wood. I assume this has something to do with the change in grain orientation. I had pore filled with the Oxford water based "high volume" filler. It didn't look blotchy before I put on the tru-oil. Can anyone advise me what causes this and if I need to sand back and start over? Thanks, Pat |
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| Author: | Chris aka Sniggly [ Tue Nov 25, 2008 10:20 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
At any stage during your finishing schedule.....did you seal? With anything I mean....vinyl sealer...shellac? The type of wood the neck is made out of would help too. Chris |
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| Author: | SniderMike [ Wed Nov 26, 2008 12:53 am ] |
| Post subject: | Re: Tru-Oil Blotchiness |
I would sand back to wood to make sure there's no glue contamination or anything under the tru-oil. Then put a seal coat of shellac on, and see how it looks. |
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| Author: | Laurent Brondel [ Wed Nov 26, 2008 5:29 am ] |
| Post subject: | Re: Tru-Oil Blotchiness |
It sounds to me like the filler on the end grain has not been sanded back enough. Typically you want to sand to 220 before putting any finish on and be very vigilant where the grain changes orientation like the heel, handstops etc. I always go to 320 or 400, and then back to 220. It allows me to see scratches I would have missed before, especially on end grain. Why a waterbase grain filler before the Tru-Oil? Also have you raised the grain a few times before applying that pore filler? I'd sand back to raw wood, lightly so as to leave the filler in the pores. |
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| Author: | Rob Warren [ Wed Nov 26, 2008 7:56 am ] |
| Post subject: | Re: Tru-Oil Blotchiness |
I've had glue spots around my side marker dots on my latest build in maple. I thought they were sanded all the way out, but after applying tru-oil, they shaw up as lighter than the rest of the neck. I would probably try sanding back to make sure all the glue or filler is off the neck. I'm no expert, only built 2, but used tru-oil on both and that's the only time I've seen it blotchy. Oh, and I think I read somewhere that for a better finish with tru-oil, the higher the grit you finish sand with the better. I went to 400 on both my builds. |
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| Author: | StevenWheeler [ Wed Nov 26, 2008 2:57 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
I just had this same problem with another brand of clear water based pore filler. From my experience, I would say Laurent's assesment is correct. You'll have to resand to remove the excess sealer. Steve |
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| Author: | Pat Hawley [ Wed Nov 26, 2008 8:31 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Thanks for the advice guys. Tonight I sanded the neck back and re-oiled. Looks good now. Then I sanded back the top to get rid of some glue spots that I hadn't noticed before. So now the top is looking acceptable. Lastly, I sanded the back and re-oiled that. Still looks blotchy. That's a bit of a puzzle because I thought I had sanded back carefully. Tomorrow night I may sand the back again and try applying a sealer coat of shellac. We'll see what happens. Pat |
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| Author: | j.Brown [ Thu Nov 27, 2008 12:56 am ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Sealing is always a good idea under tru-oil. |
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| Author: | Mike OMelia [ Thu Nov 27, 2008 11:20 am ] |
| Post subject: | Re: Tru-Oil Blotchiness |
There is a great article in a recent FWW about blotchiness andwhat to do about it. Sand to your final grit, apply denatured alcohol (careful with high oil content woods here!) and blotch areas should show up. Apply thinned shelac to seal (as others have said) and sand back. Mike |
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| Author: | Laurent Brondel [ Thu Nov 27, 2008 12:26 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Tru-oil can be used as a sealer, and obviously without sealer, it's technically a long oil varnish. No problem here, it has excellent adhesion. Wiping with alcohol (or lacquer thinner, or acetone) is not recommended when light purfling lines or veneers are present. The oils from the darker woods will smear everything. Naphta can be used, or mineral spirits. |
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| Author: | SniderMike [ Thu Nov 27, 2008 1:06 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Laurent Brondel wrote: Tru-oil can be used as a sealer, and obviously without sealer, it's technically a long oil varnish. Are you sure about that, Laurent? I was pretty sure it was just a polymerized linseed oil, without any resins. Of course, I'm wrong all the time! |
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| Author: | Laurent Brondel [ Thu Nov 27, 2008 2:59 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
SniderMike wrote: I was pretty sure it was just a polymerized linseed oil, without any resins. From the smell and colour I'd say it's tung oil based, and yes it appears to have some kind of resin. It's thin, so a lot of coats are required to obtain a decent finish but it's reasonably hard. |
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| Author: | WaddyThomson [ Thu Nov 27, 2008 4:18 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Tru-Oil is, by weight, 56% Mineral Spirits, 33% Modified Oil (proprietary), and 11% Linseed Oil. |
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| Author: | Laurent Brondel [ Thu Nov 27, 2008 5:02 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Any idea what the modified oil is? |
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| Author: | WaddyThomson [ Thu Nov 27, 2008 10:06 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
I have no idea. I looked that up on their website, in the MSDS files. |
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| Author: | Howard Klepper [ Fri Nov 28, 2008 1:09 pm ] |
| Post subject: | Re: Tru-Oil Blotchiness |
My understanding (from where, I don't know) is that the oil is all linseed, but most of it is polymerized and the smaller amount is left in unpolymerized. I doubt that they would use tung, which is more costly, and then not mention it. I don't think this should be called a long oil varnish. Its behavior is like a short oil varnish, but IMO to say long or short oil implies that there is a resin in the mix. In this case, the polymerized oil functions like a resin. |
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| Author: | Pat Hawley [ Sat Nov 29, 2008 9:48 am ] |
| Post subject: | Re: Tru-Oil Blotchiness |
Interesting discussion. Regardless of what it is, it seems to go on nicer over a shellac seal coat. I sanded back the back (again) and put on a seal coat of shellac. Then when I applied the tru-oil it looked very nice indeed. No more blotchiness. This will be my standard operating procedure for future applications of tru-oil. Thanks again for your suggestions. Pat |
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