Time for a rubbed oil finish? Or new tops?
Anyone tried baking tops like this in a oven for a few hours at 150degC prior to using (to harden the lignin/pitch/oils)?
Cheers,
Dave F.
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| Struggling with streaking in spruce tops rejecting lacquer http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=38171 |
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| Author: | David Murray [ Tue Nov 06, 2012 10:12 am ] |
| Post subject: | Struggling with streaking in spruce tops rejecting lacquer |
I've recently started using a batch of Engelmann for parlor guitars. This is my first time using Engelmann - I've avoided it up to now but saw this beautiful, shimmery batch and couldn't pass it up. I now have three in the spray booth, and they're giving me fits. My standard nitro process is 3 coats of sanding sealer, then grain fill, level, one more sanding sealer, 2 clear coat, level, 3 clear coat, level, 3 clear coat, wait 10 days, level and polish. This spruce has fine streaks in the grain, slightly darker than the grain so I assume they're streaks of resin? The only other thing they could be is some kind of void that's sucking in the lacquer, but that doesn't seem right at all. They seem to be rejecting the lacquer. So after this whole process, I still had dozens of pin holes along these streaks. I kept going, just hoping that they would eventually fill but they didn't. Now I've gone back and stripped down one, started over with shellac and pumice to fill any voids, but I'm getting the same problem this time around. On one hand, I hope none of you have dealt with this, because it's horrible! On the other, I really hope maybe a few of you have and that there's an easy solution. Thanks for any help! |
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| Author: | John Arnold [ Tue Nov 06, 2012 11:06 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
They are pitch streaks. A shellac coat to seal them is generally sufficient. I don't see much point in using pumice on spruce. The other challenge in finishing spruce is resin canals, but they usually are small enough fill up with lacquer. |
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| Author: | David Murray [ Tue Nov 06, 2012 12:35 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
John Arnold wrote: They are pitch streaks. A shellac coat to seal them is generally sufficient. I don't see much point in using pumice on spruce. The other challenge in finishing spruce is resin canals, but they usually are small enough fill up with lacquer. I wasn't into using pumice either, but thought if there was any kind of canal or void I might as well fill it on the front end. At any rate, the shellac hasn't been sufficient. I don't know how I've avoided this issue so far - have you found pitch streaks to be more common with Engelmann? Googled - "pitch streak" spruce guitar - there's not much info out there. Shorten it to - "pitch streak" spruce - and there are some recommendations to pretreat with turpentine or paint thinner. Another recommendation was two coats of shellac with a light sanding between. Thanks for the reply John. |
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| Author: | B. Howard [ Tue Nov 06, 2012 1:07 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Resin in the wood can be a finishing problem in certain woods, not just spruce. I generally give a really good cleaning with DA after final sanding on all woods under all finishes to minimize problems like this. Shellac however should cover and stick to pitch and resin no problem whether wiped down or not. |
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| Author: | David Murray [ Tue Nov 06, 2012 1:30 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Sounds good Brian, thanks. I'm adding a DA wipedown + shellac to the front end of the finish schedule then. |
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| Author: | John Arnold [ Tue Nov 06, 2012 2:31 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Pitch streaks are most common in red spruce, though I have seen them in European and Engelmann spruce on occasion. They seem to be quite rare in Sitka. |
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| Author: | Rod True [ Tue Nov 06, 2012 8:08 pm ] |
| Post subject: | Struggling with streaking in spruce tops rejecting lacquer |
David, what's your pre-finish sanding schedule??? It sounds like you know what you're doing but thought I'd check. You're not sanding any higher than P280 are you? Any higher and you could certainly have adhesion problems. |
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| Author: | David Murray [ Tue Nov 06, 2012 10:07 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Thanks for the info John. Rod, where finishing is concerned, I'm no expert. I'm always learning and I'm young enough in this that there's plenty of growing room. What's nice about a forum like this is that I don't feel pressure to prove anything even though I build for a living. Part of the issue is that I'm in India. I live in a poor community in the Himalayas, and I'm training 8 guys to build. We don't have Home Depot-style access to DA or naphtha for example, although I can get "methylated spirits" from the medical supply shop for about the same price as high end vodka (and I think it's the same thing?), or naphtha in the form of 3-ounce tins of lighter fluid. When I ask what people use here for shellac (they call it lac dana) they say to use mineral spirits, but I don't think that's right - isn't that more oily and slower-drying than DA? Sandpaper is another thing altogether - we have what they call flint paper, and it doesn't come in 280. I've been importing 3M adhesive paper from Stewmac, but I've always block-sanded to 220 toward the end of voicing, then 320 prior to finishing. Is everyone here in agreement that 280 prior to the seal coat is preferable? |
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| Author: | Rod True [ Tue Nov 06, 2012 10:36 pm ] |
| Post subject: | Struggling with streaking in spruce tops rejecting lacquer |
Some folks sand only to 220 prior to finishing, 320 is probably to high which could be part of your problem. The other could be humidity related. If you are finishing under high humidity you can also have adhesion issues, not to mention blushing of the lacquer. |
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| Author: | David Murray [ Wed Nov 07, 2012 4:13 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
We're really careful about humidity. No blushing. Guess I need to go on the lookout for 280 paper. Thanks Rod. Can a few builders weigh in with your nitro schedule? - Final sanding grit prior to pre-treat - Pre-treat process - Sealer - viscosity and number of coats - Fillers - what products give you the best results - Clear coats - how many coats, how often do you level, what viscosity do you shoot for? I'm guessing there may be another thread that has already handled this? |
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| Author: | David Murray [ Wed Nov 07, 2012 5:00 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Alright, did some searching through the forum and there are already plenty of opinions on finishing schedules. Thanks John, Brian & Rod - I'm going to be much more obsessive about our pre-finish schedule now. |
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| Author: | David Murray [ Wed Nov 07, 2012 11:11 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
I went down to the bazaar yesterday to pick up more DA - they add blue dye here to make sure you know it's poisonous. The seller also wanted me to try [i]lac dana[i], also called seedlac. Does anyone have experience with this? It comes in rough, red granules, and they recommend you add these rocks of what looks like hardened white sap to make it stick better. I'm guessing I'm off the reservation at this point - it's just that long-term, I'd love to be able to use local products for finishing, because many times I can't ship finishing materials anyway. |
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| Author: | Rod True [ Thu Nov 08, 2012 10:55 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
David Murray wrote: I went down to the bazaar yesterday to pick up more DA - they add blue dye here to make sure you know it's poisonous. The seller also wanted me to try [i]lac dana[i], also called seedlac. Does anyone have experience with this? It comes in rough, red granules, and they recommend you add these rocks of what looks like hardened white sap to make it stick better. I'm guessing I'm off the reservation at this point - it's just that long-term, I'd love to be able to use local products for finishing, because many times I can't ship finishing materials anyway. Get some and test it out, that's your best answer and then YOU'LL know if it'll work or not.... |
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| Author: | B. Howard [ Fri Nov 09, 2012 5:37 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
The seedlac will need de-waxed if you intend too use it as a sealer under lacquer. Not sure what the other substance you mention is, most likely some other resin. Sandarac perhaps, but you do not need it. If you are interested in doing a local finish, how about French Polish? |
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| Author: | David Murray [ Tue Nov 13, 2012 1:49 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Alright, stripped all three 00's down, dewaxed shellac coat, all the way back through build coats & leveling and I still have pinholes at the pitch streaks. Any other options at this point? There are hundreds of them, so I wasn't keen on drop filling, but I'm guessing that's my last resort? |
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| Author: | B. Howard [ Tue Nov 13, 2012 5:34 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Did the pinholes form in the shellac? |
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| Author: | David Murray [ Tue Nov 13, 2012 9:03 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
They weren't visible until about 4 build coats in. I assume they were there all along. I'll try to get some pics and post them - let me know if you'd had luck filling this sort of thing. |
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| Author: | David Murray [ Fri Nov 30, 2012 4:55 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Update: four guitars in the finish booth and all are struggling with this same issue. I won't be using Engelmann spruce again. Still need advice from anyone with expertise in this. For the 4th guitar, I started with 5 coats of shellac (dewaxed, from Stewmac). I could still see the pits forming over pitch streaks. I've begun to apply lacquer, and the lacquer literally runs away from the pitch streaks. For the other 3, each has been though the full nitro schedule and each still has pinholes over the pitch streaks. I have tried overcoating with melamine and with varnish, and both run away from the pitch streaks. I'm now considering going back to shellac. I can't scrape back down to bare wood at this point. I've already done that once and doing it again would mean getting the tops thinner than I'm comfortable with. So I'll try a dozen coats of shellac over leveled lacquer, polish it out and see what happens. Please - I would love some help or advice at this point. |
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| Author: | B. Howard [ Fri Nov 30, 2012 5:42 am ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Based on your descriptions I don't think it's actually sap or pitch. Is it possible that your wood was contaminated with oil, silicone or some other contaminate? Maybe prior to your purchase? Shellac will absolutely stick to and seal pine pitch, I have been sealing knots and pitch pockets with the stuff my entire career and finishing over with all manner of coating without any thing like you describe happening. |
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| Author: | Ken Grunst [ Tue Jan 01, 2013 2:41 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Advice, please. I have two beautiful fine-grained Carpathian spruce tops on guitars that I'm spraying and I have developed the same problem with pitch. Sanded both tops with 220 grit and then first sprayed both with several coats of Seagrave Vinyl Sealer. After several days I sanded and leveled both tops. Then I sprayed two coats of Seagrave Gloss Lacquer and bubbles showed up in numerous spots on both tops along the grain lines. So I sanded both tops down to bare wood and started over with three coats of dewaxed shellac per this thread. Both tops looked great and no longer saw any bubbles, so I sanded both tops smooth and began to spray lacquer again. One top looks great. The second top now has bubbles in several spots. Minor amount, but I don't believe more lacquer is going to solve the problem. My suspicion is that I sanded through the shellac in several small areas and didn't know it. QUESTION. Now that I have one coat of lacquer over the shellac, do I have to remove ALL the lacquer from this top before I spray a couple coats of additional shellac? Or, can I just sand the affected areas, lightly sand the rest, and then spray the shellac? First time I've ever had this happen. I would appreciate your advice. Ken Grunst Williamsburg, VA |
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| Author: | B. Howard [ Tue Jan 01, 2013 6:14 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Shellac should stick to the lacquer. I would simply concentrate on the problem areas rather than putting shellac over the entire surface. |
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| Author: | Ken Grunst [ Tue Jan 01, 2013 6:22 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Thanks, Brian. I was afraid noone would see this entry at the end of an old thread and needed some information tonight so I could spray tomorrow, so I also started a new post. (must have posted it at the same second as you posted your reply) I've sanded the entire top pretty thoroughly and all the lacquer may be totally removed but I don't know any way to tell for absolute sure, and I sure didn't want to have a finish failure on this one. I appreciate the suggestion. I'll give it a try. Ken |
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| Author: | Mike OMelia [ Tue Jan 01, 2013 7:41 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
What about painting heavy strips of shellac along the streak lines? Or covering the top in a clear epoxy? If you notice the epoxy pin holing, then as it starts to set (thick state) use a razor to work the epoxy Mike |
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| Author: | Dave Fifield [ Tue Jan 01, 2013 9:14 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Time for a rubbed oil finish? Or new tops? Anyone tried baking tops like this in a oven for a few hours at 150degC prior to using (to harden the lignin/pitch/oils)? Cheers, Dave F. |
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| Author: | Ken Grunst [ Tue Jan 01, 2013 11:10 pm ] |
| Post subject: | Re: Struggling with streaking in spruce tops rejecting lacquer |
Hi Mike and Dave: I thought about taking the top down to bare wood and using epoxy. I actually had epoxy on the top to level pearl rosette and pearl purfling, but pretty much sanded it back to bare wood before I got started spraying. Unfortunately, I'd have to take it back down to bare wood again if I were to epoxy the entire surface. Mike...I am pretty sure that more shellac will solve the problem, but I didn't know if I could apply it if there were any traces of lacquer remaining on the top. That was my concern...would shellac fail if there was any lacquer at all over the shellac. I've sanded the top pretty thoroughly I also considered a small touch up right at the flaw and touch it up with shellac, much as you suggested, except that now that I've sanded it quite thoroughly, I'm not sure I can find the exact flaw area unless I spray it again with lacquer. and then I'm sure it would show up again. Dave...I just can't bring myself to putting this guitar in the oven...no matter how low the temperature. Besides...my wife would KILL me. HA! I think it might be a good idea to try cooking a new set before I get started...Taylor does something similar with their tops, I understand. I've got quite a few sets of Carpathian Spruce left to build and hopefully won't have to face this problem again. Are either of you comfortable with spraying the top with several more coats of shellac over this sanded shellac/lacquer top? Thanks much for your replys. These are two pretty guitars with pearl purfling. I don't want a finish failure. Ken |
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