Final Buffing Steps for a Guitar Finish
Advice on how to go beyond fine-grit sanding and remove fine scratches. January 27, 2007
Question
We are using the Satin Krystal Clear from ML Campbell. After we spray it to final thickness, we scuff sand to make it level. After leveling, we spray one final coat (that is nearly perfectly level) and sand starting with 1000 grit going up in increments of 200, stopping at 2000 (i.e. 1000, 1200, 1500, etc.).
Then we rub on an automotive wax to remove the super fine scratches and to make it slightly more vivid. There are very fine scratches in the finish after we do this. Since our product is very small and needs to look perfect, we can't have these fine scratches it's leaving. Is there a way to remove these? Would using the buffing arbor do the trick? (We use the buffing arbor on our gloss finishes and it seems to work fine.)
Forum Responses
(Finishing Forum)
From contributor J:
Sand only by hand and stay with the grain. Use only a stearated paper and
change your sandpaper often to avoid "corning" (small bits of finish that stick to the paper). This can leave scratches that are much deeper than the grit you are using.
From contributor R:
I'm assuming you don't want high gloss? I would try Mirka Abralon pads on a sander. These pads come in grits from 180 to 4000 and it is very difficult to find the scratches except on something very dark or black.
From the original questioner:
We are wet sanding by hand. There is no corning on the paper.
We cannot use a power sander since our product is guitars (many small edges/corners). So, we are already doing everything suggested here. Any other thoughts on this?
From contributor R:
You could use a power sander on the large flat areas and then hand rub out other areas using Mirkas' sanding pad.
From contributor W:
I'm thinking you might want to progress further than the 2000 grit you're using now by hand.
From contributor T:
Don't quite understand an objection to micro-scratches on a satin finish, but... three alternatives:
Before you wax, rub out the finish with a 3 step rubbing compound. There are many products to do this, but automotive rubbing and polishing compounds work fine.
After your 2000, switch to Micro-Mesh. It was originally developed to remove scratches from Plexiglas and goes on up to 6000 or 12000 - I forget. Water as a lube.
After your 2000, polish with Glanz Wauk (sp?) on a slow turning, loose buff. It's a white polishing compound (from Germany I think) that golf club makers used to use to polish wooden golf club heads. I've had a big stick forever that I got from a golf club construction materials/supplies company. I use it on a loose buff chucked in my lathe and turning at slow speed, but I'll bet a wool buffing pad on a slow turning polisher would work too. Careful not to over heat - makes a mess of thermo-plastic things like lacquer.
From contributor M:
You mentioned that you use an automotive wax. I think you should be using a fine polishing compound to remove any fine scratches that are left over.
From contributor E:
Is the Satin Krystal Clear compatible with the Menzerna polishing system? Piano manufacturers use it. We know how good the grands look.
From contributor C:
Several points for you to consider: The grit is only half the story. 100 grit with sponge backer will give a similar scratch pattern to 150 grit with paper backer... The grit fracture pattern can vary quite a bit. 3m's sandblaster and Norton's 3x are superior quality grits which cut more like tiny plane blades as compared with some el cheapo grits that I have used, which cut more like coarse wire brushes. When you get to about 500 grit or finer, you really need a soft sponge backer to get the effect that you are looking for. Sanding is not very effective even when done with great skill for developing final sheens... It works best as early steps toward the desired sheen. Final sheens are better done with steel wool or various rubbing/polishing compounds or pumice/rottenstone pastes. I've had very good results using soft scrub cleansers for satin sheens (scrubbed with damp rags). Soft scrub cleansers have whiting as the abrasive component.
The Abralon pads, folded in half, make excellent hand sanding pads. A satin sheen product is not ideal for rubbing out due to the (likely) inclusion of flour silica as a flatting additive. This makes it softer and spongier, less likely to achieve a mechanical sheen that is very consistent. I do satin sheens regularly and rarely rub out the final coat. If you have a nice level surface for the penultimate coat, a final satin coat straight off the gun is a reasonable expectation. High gloss is another story, though.
From contributor J:
Penultimate coat? Is there more to this than merely final coat?
From contributor C:
Penultimate is one tier down from ultimate, in other words, the next to final coat. I am saying that with a nice smooth and level base your final (sheen establishing) coat should be smooth, wet and wonderful straight from your gun and require no further steps, at least for satin sheens. High gloss varies more and, while I have heard of great high gloss finishes straight from the gun, I have yet to achieve them.
From contributor I:
No one has mentioned wet sanding.
