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Solid-color block sanding

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Solid-color block sanding

Postby Steve Sawyer » Thu Jul 27, 2017 8:54 pm

As I just mentioned in another thread, I'm dodging the humid weather to get the color coat laid down on the body of the tele I'm working on. I just block-sanded the first coats, and was wondering if I need to remove ALL of the shiny spots before moving on to the next coat. I'm trying not to sand through the color too much, so I'm trying to keep a very light touch. I've got it pretty level, but there is a scattering of shiny orange-peel dips, particularly near the edges where I'm most likely to sand through. I just ordered another can of the base color from ReRanch, so if I have to be more aggressive, I won't run out of the color if I have to correct a few more sand-throughs. So far, I've only got about four little sand-throughs where I think I may not have put on as good a coat (e.g. up around the horns).

Thanks.
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Re: Solid-color block sanding

Postby Alan Carruth » Fri Jul 28, 2017 12:00 pm

I don't do opaque solid colors, but have some experience with varnishing violins. The best plan I've found for those is to get the surface level before you start the color coats. Of course, in that case an uneven thickness gives a change in color, which is not a problem for you. Still and all, I'd say that since you'll have to get those cat's eyes out anyway, the sooner the better. In the end, the finish is only as good as the surface it's on, and time spent in surface prep is well spent.
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Re: Solid-color block sanding

Postby Steve Sawyer » Sat Jul 29, 2017 12:41 am

Alan Carruth wrote:The best plan I've found for those is to get the surface level before you start the color coats. Of course, in that case an uneven thickness gives a change in color, which is not a problem for you. Still and all, I'd say that since you'll have to get those cat's eyes out anyway, the sooner the better. In the end, the finish is only as good as the surface it's on, and time spent in surface prep is well spent.

The surface was level before applying the color, Alan, and sanded to 320. What I'm working on is some orange-peel-like surface imperfections in the finish. My thinking is that the next coat is likely to suffer the same imperfection, and more than likely filling the existing shiny spots and introducing new ones after level-sanding. After repeating this three times, I'll be much less concerned about being aggressive and removing all of those shiny spots before progressing to the clear-coats, as I'll be less likely to risk sanding through the color at that point.

Just looking for confirmation that my thinking is correct, or a dope-slap that I should get ALL of the imperfections out of every coat, and damn the sand-throughs. Maybe my first coat (three shoots over the course of an hour) was too thin. My plan on the next coat is to shoot extra on those areas where I sanded through to compensate.
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Re: Solid-color block sanding

Postby Barry Daniels » Sat Jul 29, 2017 11:38 am

For future reference I recommend figuring out how to spray without getting orange peel. You really don't want to be sanding on color coats at all. No pro finishers that I know ever do that except for a scuff to aid adhesion of next coat. Sanding on sealer coats will get the surface flat and sanding on clear coats is to get the final surface smooth. Color coats are kept thin and low in number to prevent the final finish from being too thick.
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Re: Solid-color block sanding

Postby Steve Sawyer » Sat Jul 29, 2017 7:27 pm

Barry Daniels wrote:For future reference I recommend figuring out how to spray without getting orange peel. You really don't want to be sanding on color coats at all. No pro finishers that I know ever do that except for a scuff to aid adhesion of next coat. Sanding on sealer coats will get the surface flat and sanding on clear coats is to get the final surface smooth. Color coats are kept thin and low in number to prevent the final finish from being too thick.


Thanks, Barry - I didn't realize that. I'll see what I can do on the next coat.
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Re: Solid-color block sanding

Postby Brian Evans » Sun Jul 30, 2017 10:08 am

Remember that the reranch colors are nitro cellulose so the subsequent coats will melt into the existing, and should take care of the orange peel. I would probably have 2 or 3 goes of three coats each of color, then the same of clear, then wait three weeks and then start to sand/polish.

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Re: Solid-color block sanding

Postby Steve Sawyer » Sun Jul 30, 2017 12:59 pm

Brian Evans wrote:Remember that the reranch colors are nitro cellulose so the subsequent coats will melt into the existing, and should take care of the orange peel. I would probably have 2 or 3 goes of three coats each of color, then the same of clear, then wait three weeks and then start to sand/polish


Okay - thanks, Brian!
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Re: Solid-color block sanding

Postby Gordon Bellerose » Sun Jul 30, 2017 10:32 pm

I don't use nitro, only water base products, but the differences in technique are not large.

If I get a rough patch or orange peel in a color coat, I simply sand it down smooth and re-coat the color.
As long as you're not laying it on too thick you will be ok.

Yes. The sand throughs are almost always on the edge.
I need your help. I can't possibly make all the mistakes myself!
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