Haze after wet sanding

The Achilles' Heel of Luthiery
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jdb
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Joined: Sun Oct 17, 2010 8:53 am

Haze after wet sanding

Post by jdb »

First of all, I am new to this forum and this is my first post. I have managed to make it to the finishing stage of building my guitar without many problems. I have applied all the finish according to a mix of instructions from various places. Now I am to the wet-sanding stage with 1200 grit paper. My question may be due to ignorance as I don't know what to expect. When I am sanding, it is turning hazy (don't think it is blush as I dealt with that earlier). So, my question is will this go away with polishing or am I doing something wrong?
tippie53
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Re: Haze after wet sanding

Post by tippie53 »

welcome to the forum .
What finish are you using ? Also is this haze or just a surface scuffing ?
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
jdb
Posts: 10
Joined: Sun Oct 17, 2010 8:53 am

Re: Haze after wet sanding

Post by jdb »

I am using nitro-cellulose out of the spray can. The best I can describe it is that it looks like a foggy windshield. It will clear up temporarily when it is wet or when I wipe up the excess water from wet sanding but will come back. I have seen blush from previous sprays that went away with a blush eraser and it doesn't look quite the same. Before my final sanding started, the finish looked clear. I am hoping it is a normal thing that will come out with polishing.
jdb
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Joined: Sun Oct 17, 2010 8:53 am

Re: Haze after wet sanding

Post by jdb »

I am using nitrocellulose spray cans. The haze is a lot like a foggy windshield and it goes away when wet from the wet sanding but then as it dries it will come back. It could be normal and will go away with the polishing but I just wanted to be sure.
Tony_in_NYC
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Re: Haze after wet sanding

Post by Tony_in_NYC »

That's normal. It's the scuffing of the finish. It will go away as you work up through the grits of sand paper and then polish.
tippie53
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Re: Haze after wet sanding

Post by tippie53 »

If you are using the can's allow a bit more time. You need to let this cure . I don't touch lacquer for 3 weeks after I spray. This allow it to cure and shrink and will give you a better finish. When it comes to finishing ,Prep and patience is key
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
jdb
Posts: 10
Joined: Sun Oct 17, 2010 8:53 am

Re: Haze after wet sanding

Post by jdb »

Thanks for the help. Part of my problem was not sanding enough. I have been intimidated by the warnings of oversanding and now I realize that I was being too light. As I get the surface smoother and all the low spots out, it is starting to look more like I expected.

I have seen some other posts about using waterbased finishes which I was leaning towards on my next project. How do their curing times differ from nitro? Also, do waterbase finishes hold up like nitro? What are the pros and cons between the two?
Darryl Young
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Re: Haze after wet sanding

Post by Darryl Young »

jdb, I'll try to answer a few of your questions but the info I'm giving you is based on reading only (I've not yet finished my first). Water based lacquer takes approximately the same length of time to cure as nitro based lacquer. It might be slightly faster but it's likely better to wait 3 weeks between the last application and sanding/polishing. Seems I have read some folks wait 2 weeks so it may cure a bit faster. One down side of waterbased lacquer is sometimes the acrylic base shows a blueish cast when in good or natural light.

Another water base option is KTM-SV which is a spar varnish. It cures a little bit harder so gives a little more protection and it cures faster.......sand through the grits 2 days after application and buff 7 days after application. The downside is this finish doesn't burn in as good as lacquer so repairs may not be hidden as easily or you may want to respray the whole surface per chance you need to repair (example, if the back gets a big ding damaging the finish, you could repair that small area only but it possible you may have witness lines around the repair.......or instead, you could resand the entire back and reshoot the whole back so you wouldn't have the witness line).

For my first, I trying the KTM-SV. We will see how it goes.
Slacker......
jdb
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Joined: Sun Oct 17, 2010 8:53 am

Re: Haze after wet sanding

Post by jdb »

Very helpful information. Thanks Darryl.

I am almost done with my first and am using nitro. I have been nervous the whole time just because of the dangers of nitro. I am working on mine on the side so you may finish before me. :)

I would like to see some pictures of yours when get done.

Thanks again!
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