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Finishing torrified sitka spruce...
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Author:  flemsmith [ Mon Jan 03, 2022 2:46 pm ]
Post subject:  Finishing torrified sitka spruce...
Third guitar. First try with any top that's been thru the torrification process. Good news is the top has some great looking bear claw.

Have about 10 coats of lacquer on, level sanded to 2000. Back looks beautiful. Bad news is the top in the sun looks like it needed pore filling, which I've never done on a top. Not sure what to do now. No way it's gonna polish up well that I can see.

Sand the top more agressively, pore fill (Z-poxy) and respray? I typically can not tell whether pores are totally filled while sanding with the rougher grades, then it shows up as I get to the 800 and above grades. Still have some of that issue on the sides.

I did purchase some marine epoxy, but have not used it yet.

Thanks in advance for any suggestions.

Roy
Author:  Barry Daniels [ Mon Jan 03, 2022 3:21 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
There aren't any significant pores in spruce. Must be something else going on. Can you get a close-up photo of the problem?
Author:  flemsmith [ Mon Jan 03, 2022 8:28 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Close up photo....Mebbe, but it's only noticeable when reflecting sunlight off it. I'll try tomorrow.

I know it shouldn't have 'pores' but there's some definite little vacant looking "tiny threads" all over the top now that it's levelled and sanded thru 2000 grit. To feel it with fingertips, it seems just as smooth as the back, but the reflected view is not nearly as shiny as the back.

Not sure why I need to try doing something new every time, but that seems to be my MO. Thanks for the interest.
Author:  flemsmith [ Tue Jan 04, 2022 12:54 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
This is the best pix I could get. It's obvious if you blow it up, but I doubt you can do that when I post it here. It feels perfect, but if you look at the bottom right edge of the reflection, you can sorta see a few tiny gaps in the wood that show what I'm talking about. They are pervasive all over the top. It was sanded to 360 before I started the lacquer, first coat was the Cardinal vinyl, then I let the lacquer cure for about 3 weeks...ask que's if I left out any info that might help. Surely someone else has finished torrified tops before....Roy


Image
Author:  Barry Daniels [ Tue Jan 04, 2022 1:38 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
I enlarged it to the max, but I can't see anything. Can you get a closeup or macro photo of it? Do you know any finishers (auto, cabinet makers, etc.) in the area that could give you advice? You have had a lot of problems with your finishing that makes me think there is something we are overlooking.

For example, I once knew a violin maker and he was having his coats of varnish peel off like onion skin from the previous layers. My boss spent an hour with him going over every step in his finish routine. Turned out he was not using a traditional tack cloth before each coat, but some dusting cloth he had bought at Wally World. The dust cloth was saturated with silicone.
Author:  John Arnold [ Tue Jan 04, 2022 2:20 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Resin canals can do this, and it looks like there are a lot in that top.
I would just spray more lacquer and level sand.
Sitka has larger resin canals than the other spruces.
Author:  Ken Nagy [ Tue Jan 04, 2022 5:56 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
It seems to me that spruce is very hard to get smooth. Flat? Yes. Smooth? No. I OBVIOUSLY don't put on nearly enough varnish for the bowling ball finish. The soft/hard grain lines, even with repeated wet sanding and dry sanding, always show up. I like the look myselve, and on bowed instruments, excepting new Chinese instruments, it is pretty much the norm.
Author:  SteveSmith [ Tue Jan 04, 2022 6:24 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
I’m with Ken, I finished my torrefied red spruce with French polished Royal Lac over a couple of plain shellac seal coats. It’s not perfectly smooth, it still looks like wood. I like it that way.
Author:  flemsmith [ Tue Jan 04, 2022 9:49 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Since I'm already into this with Nitro, what is the downside to just spraying the top some more like John suggests? I was expecting to be able to get it at least as shiny as the last one, a cedar top. Mebbe I'll take it to the automotive paint supply shop and see what he thinks... Roy
Author:  SteveSmith [ Tue Jan 04, 2022 9:54 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
I would follow John’s advice.
Author:  flemsmith [ Wed Jan 05, 2022 2:19 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
As long as I'm showing my finishing ignorance anyway, and since I've sanded thru on the sides a bit, I need to ask about whether I should do a light sanding at a rougher grade to make sure I don't have adhesion problems as I'm planning to spray all over rather than just the top. 600 grit? lower?

Roy
Author:  John Arnold [ Wed Jan 05, 2022 4:07 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
I dry sand with 220 between coats. The same with the bare wood. The main concern is that the bare areas may show a different color because of using a finer grit than originally used on the bare wood. You can test to see if that is the case by wiping with naphtha. With lacquer, there is no concern with adhesion to the previous coats regardless of the grit used, since the solvent in added coats will melt into it. That is called 'burning in'.
As the lacquer ages, the melting in from spraying additional coats will become less, to the point where eventually you may get witness lines. But in normal circumstances, that will take weeks.
While the auto paint store can be a valuable resource (I used automotive acrylic lacquer on guitars for years), they are not experts at finishing porous surfaces, and these days, the primary 'clear coat' that is used in the automotive refinishing trade is catalyzed urethane.
Author:  flemsmith [ Sun Jan 09, 2022 9:23 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Finally got lacquer on it, 3 coats will be about 2 weeks before level sanding again. Need to ask about sanding sides. I'm using a 3" Mini Swirl Killer with flex pads, except the 600, which pads are thin like screen door material. I sanded thru a few spots on the side. So long as I make sure I'm using the flex pads thru all the grits, should I be ok on the sides? Nervous there.
Thanks, Roy
Author:  Colin North [ Mon Jan 10, 2022 3:44 am ]
Post subject:  Re: Finishing torrified sitka spruce...
Just to be clear, are you using the 3" Mini Swirl Killer with abrasive discs to level nitro lacquer?
Author:  Barry Daniels [ Mon Jan 10, 2022 9:32 am ]
Post subject:  Re: Finishing torrified sitka spruce...
I have one of those Mini Swirl Killers but I do ALL of my in-between-coat sanding by hand. Easier to control and prevent sand throughs. The only time I do any power sanding is when I get into final coat sanding stages above 1000 grit. And even there I do not use it on the sides.
Author:  Colin North [ Mon Jan 10, 2022 10:51 am ]
Post subject:  Re: Finishing torrified sitka spruce...
I'm using a very similar polisher, and I have a couple of observations.
One is that these polishers are not made for sanding (no extraction so dust will build up, ball up and leave scratches) and the other thing is that even on it's lowest speed it feels like it would be really harsh with abrasives, especially on curved surfaces like sides, and definitely with thin finishes like nitro.
I hand sand everything, top, back and sides, level up to 1200 grit, and use an ROS only for higher grits, saving the polisher for buffing.
Author:  Barry Daniels [ Mon Jan 10, 2022 11:32 am ]
Post subject:  Re: Finishing torrified sitka spruce...
When I use the polisher for the higher grits, I use a bit of soapy water on the sanding pad.
Author:  flemsmith [ Mon Jan 10, 2022 2:55 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
OK, thanks. That's all good input.... Although by hand is how I was trying to begin with, results not so good on 1st guitar. I totally agree on the sides, I just need to learn how to tell better that I've got each grade completely finished with no scratches from the previous (seems like with different directions for each grit I shouldn't have any trouble....) On the top and back, I was using 600 and above with the Mini, little to no pressure, and it's better than what I was getting by hand. I do use soap.

Back to original torrified topic, here's a pic after 3 more coats of nitro, no sanding. To me the little 'veins' look worse than the picture shows...
Image

At this stage all I know to do is to carry on and see how it looks.

Still trying to work on finish repairs of the first guitar, it got more nitro too. Mebbe I'll start the levelling process on it.

Again, thanks for being willing to help a beginner. Roy
Author:  Barry Daniels [ Mon Jan 10, 2022 3:19 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
The photo is showing orange peel. This is caused by an incorrect mixture of air to finish. Need more air or less liquid coming out of the gun. I am not sure what the lines are caused from. Haven't seen that before.

Can you tell me again the brand of lacquer? Also, please describe how much thinner you are adding.
Author:  Colin North [ Mon Jan 10, 2022 3:48 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
As Mt Arnold said, could be resin canals, I've not come across them myself, or at least they've never caused me any problems. I spray water based EV, about 29% solids - top coat is 3 x 3 mill wet coats. so nearly 3 mill dry after leveling base coats.
A 3 mill seems to be plenty to play with for final leveling and buffing.
Author:  phavriluk [ Mon Jan 10, 2022 4:08 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Taking the risk of being corrected by somebody who knows the topic, I see this guitar top as needing its finish scraped between nitro applications, else the irregularities will remain evident no matter how much finish is applied. scraping/recoating will eventually give a level and smooth surface without buildup of finish.
Author:  flemsmith [ Mon Jan 10, 2022 6:29 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
it's Cardinal lacquer and thinner. About 20% thinner, mebbe 5% retarder, which is another brand, I forget, but all from LMI. I don't know about orange peel, but then I dunno how smooth it should be after spraying and certainly not used to retuning the spray gun. I do think that the veins are well under the lacquer, because when I first tried to finish sand up to 2000 it seemed just as smooth as the back which looked and felt great. Do I take the top back to bare wood? That was my original thought when I asked about pore filling....
Author:  Barry Daniels [ Mon Jan 10, 2022 7:14 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
When spraying, I use reflected light on the surface to tell me what the lacquer is doing. The goal is a "wet coat", which looks like a mirror. The lacquer forms a completely wet surface that self-levels and burns into the previous coats.

Orange peel is basically like a bunch of wet globules that don't really bond together. So you end up with a pebbly surface composed of separate blobs of lacquer. You won't get very good burn in, and it does not self level. You will never get a decent finish until you figure this out, and you can only do that by tweaking the knobs on the gun and trying different settings. Otherwise you will just keep getting the same unsatisfactory results. I think the best way to do this is practicing on scrap instead of trying to figure it out on a real project.

One other question I would have is what is the needle size of your spray gun. I finally figured out that the guns that had been recommended to me had too small of a needle. When I moved up to a 1.6 mm I got much better results.
Author:  flemsmith [ Mon Jan 10, 2022 7:30 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Allright, thanks to all...I do know what orange peel looks like in a car finish. Since I've currently used all my lacquer, I think I may try working on the finish (repair) of #1 before I do anything to #3. On that one I was trying to fill some poor adhesion gaps around the bridge location when I removed it. Seems like it burned in fine. I'll see if I can actually level it now (or after it cures a week or so?)... when I get more lacquer, I'll experiment on some of my left over spruce pieces. Roy
Author:  flemsmith [ Tue Jan 18, 2022 4:51 pm ]
Post subject:  Re: Finishing torrified sitka spruce...
Finishing in general, I did do the repair work on Number 1, (posted an update in the repair thread) and as part of that, I resprayed a bit on the back and sides. Started sanding and compounding the back, it's better than I've typically done, but when I look at it in the sun reflection, I can see tiny spray droplets that indicate Barry is right, I dunno how to properly tune the Harbor Freight spray gun I'm using. I can also tell that I have some 800 grit scratches I didn't see well enough to remove when I went to 1000. After final polish, they are subtle but clearly visible. Ignore the side, they still need attention.
Image
I did get more lacquer, so I have some raw and torrified cedar and spruce samples I will use to experiment finishing with my usual lack of speed. I should be able to tell when in the process the torrified spruce start showing the 'veins' that have #3 build on hold til I figure out how to deal with it.
Roy
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