Fixing Sand Throughs

[CudBucket]

I was sanding my project guitar tonight. Did the 400 grit, levelled nice. Went to 600 and I think I see the beginning of 2 or 3 sand throughs on the tip of the upper horn. Didn't notice it right away because I'm sanding with MS and the body was wet. On the mahogany cavity covers, I did this on the edges and rather than sand all the way back and start over, I just dabbed some more dye on the area, cleared, and sanded.

I was just wondering what you all thought. These areas are very very small still. About 1/8" to 1/4" in diameter.

Thanks.

Dave

[thegarehanman]

Best thing to do is to try and go the easy route(assuming it's reversable, which in your case it is) and if that doesn't work, do it the hard way. I would have done exactly what you did, touch up the dye and clear everything. The clear wasn't buffed when you layed on another coat was it?

[Devon Headen]

You can try spot touching it up, but if it's dyed you'll probably have trouble getting a perfect match. And my guess is you're gonna wind up chasing sand throughs around for a bit.

[CudBucket]

No, no buffing on anything yet. Devon, why do you think I'll have more sand throughs? I've avoided them to this point (except on the cavity cover).

Thanks guys.

Dave

[Devon Headen]

If it's just on corners you might not, but if it's on a flat section, the areas adjacent to the sand throughs are going to be thin and prone to sanding through. Especially since you have several grits plus buffing to go through still. Like I said, if the corners are where you have problems, you probably won't chase it around. Don't wet sand any more than you absolutely have to on corners so you can keep a good build for buffing.

[Southpa]

Here is what I've learned. After applying dye I have no reason to sand. I like poly clear coat more than laquer clear. However, sandthrough on poly is no fun to fix, laquer is more forgiving. I'm in the process of clearcoating my tele right now with poly and am in no rush. Each shooting session involves 3 applications, then I wait a week. I then wetsand the flats with 400 grit and the edges / corners with 600 grit... very lightly, just enough to scuff so the next layer bonds better. If I see ANY dye color in the wetsanding "juices" you WILL hear me cursing from very far away!

So far I've got 2 sessions in and plan on 3 more until the poly is so thick I can wetsand to my heart's content (within reason) without any worries.

Edited July 27, 2005 by Southpa

[CudBucket]

Gotcha Devon. Well in that case, I'm lucky. No sand throughs on the flats. Just the corners.

And you see, here's the thing. I didn't see any color in my wipe downs with a clean paper towel. Only after I dried off the body, did I notice the very beginnings of the sand through. I think I'll be able to fix it OK. I just am pissed that I'll have to spray and wait again. I really though I was close to done.

Thanks guys.

[thegarehanman]

You give the poly a whole week before scuffing up? You are one patient man. All of my experiences with two packs have been very good. I leave it out in the louisiana heat and in two days max it's hard enough to be scuffed and have more sprayed on.

[LGM Guitars]

You give the poly a whole week before scuffing up? You are one patient man. All of my experiences with two packs have been very good. I leave it out in the louisiana heat and in two days max it's hard enough to be scuffed and have more sprayed on.

←

You assume he's using 2 part Poly. Most guys here aren't set up to spray 2 part poly and talk typically about stuff like the minwax poly which is a one part.

The funny thing is, if you're waiting 2 days between coats with 2 part, you're going to have adhesion problems, you'll have to be sanding with 400 to get really good adhesion, 2 part poly's really should all be sprayed in one session, if you need to respray, make sure you are sanding thoroughly before recoating.

[thegarehanman]

Yeah, I use 400 or 600 between days. Normally I try to do it all in one session, but sometimes it just doesn't work out that way. Like I said, I've never had a problem with two packs. I've sprayed a lot of the stuff. I've done two cars, two guitars, a few amp cabs, and a bunch of other odds and ends.

[LGM Guitars]

LOL, A lot, 2 cars, 2 guitars and some amp cabs, sounds like a regular week to me just teasin ya, I've already gone through over 50 gallons this year on guitars and bikes and that's just the clear

[Southpa]

Yeah, I'm just a rattlecan man.

[thegarehanman]

50gallons/week? I certainly hope you have some serious resperators and masks. Otherwise you're going to have cancer in about...meh...a week. Come to think of it, I think I already saw your setup on your site.

[LGM Guitars]

no, you read wrong, 50 gallons this year so far, I don't think there's enough hours in a week to spray 50 gallons a week LOL, I do have the protection, this is my job I have a full paint booth with all the forced air respirators, been doing this a long time now I've probably put 35 or 40 thousand dollars into my paint shop alone in the last couple years, everything is done to meet health and safety codes no worries there, I pretty much know the paint inside and out

edit: fwiw, cancer isn't so much a concern with the 2 part paints as blood poisoning, and respiratory failure, it also affects and destroys your nervous system. The isocyanates are only a possible carcinogen, meaning they can't even be classed as "suspected" at this time, probably only because they'll kill you in other ways faster than the cancer could possibly set in