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sanding shellac before sealing?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=24677		 Page 1 of 1
Author:  James W B [ Thu Nov 19, 2009 6:30 pm ]
Post subject:  sanding shellac before sealing?
I was wondering how well everyone sands shellac before the finish coats go on and with what grit paper.I`ve been using 320.It seems it leaves tiny scratches if I turn it in the light just right.Wondering if finish will hide these.Also is there a reason to wait a couple days before shooting finish over shellac?
James
Author:  James W B [ Thu Nov 19, 2009 6:52 pm ]
Post subject:  Re: sanding shellac before sealing?
Oops I meant sanding shellac before finising.
James
Author:  woody b [ Thu Nov 19, 2009 8:30 pm ]
Post subject:  Re: sanding shellac before sealing?
Disclaimer: The way I do things isn't necessarily the best or and it's not the only way.

I sand with 320. If you've got scratches it could be from build up on your paper, or sanding too hard. I use almost no pressure, especially when sanding shellac. I let it sit overnight, but I don't know if that's necessary.
Author:  Michael Dale Payne [ Fri Nov 20, 2009 1:54 pm ]
Post subject:  Re: sanding shellac before sealing?
i lightly sand with 000 steal wool prior to appling finish. you just need a little tooth to insure good adhesion if using a waterborne. You reall dont need any if using nitro because the solvent will slightly melt the shellac but i do it anyway or at least very lightly wipe with alcohol just before spraying the first coat of finish.
Author:  Mike Collins [ Fri Nov 20, 2009 2:51 pm ]
Post subject:  Re: sanding shellac before sealing?
James you need not scratch the shellac .
Unless you have to sand out a piece of dust or such.
Waterbase will melt into Shellac just like lacquer.
Because alcohol will soften waterbase & shellac.

If you have deep scratches in the wood then those have to be removed first-I'm sure you know .

Any scratches in the Shellac only will be filled and melted by the top coats.
There is no reason to wait 2 days - If you use a good denatured or drinkable thinner then you can top coat after 1 hour-unless you put way to much of a film on .
Or the humidity in your shop is above 55%. [:Y:]
Mike

.
Author:  James W B [ Fri Nov 20, 2009 5:31 pm ]
Post subject:  Re: sanding shellac before sealing?
I wasn`t aware that waterborne would melt into shellac.I hope this isn`t a problem with Zinnser seal coat.I read on the Target forum that there were problems with the shellac cracking under Em 6000.I let the shellac dry overnight and sanded it with 400 the next day.I shot 5 coats of em 6000 today and everything looks good.I`m not sure when this cracking is supposed to appear ,I hope it`s fine.It seems that de-waxed shellac flakes don`t have this problem .Next time I`m gonna do that .I`ll keep everyone posted on how this turns out.
James
Author:  Mike Collins [ Fri Nov 20, 2009 6:02 pm ]
Post subject:  Re: sanding shellac before sealing?
James ;you shot 5 coats today?
I hope they where thin ones & 2 hours apart at least !

Shellac will NOT crack unless it was applied to thick and NOT allowed to cure before overtopping.

Keep us posted .
Mike
Author:  Andy Birko [ Fri Nov 20, 2009 7:34 pm ]
Post subject:  Re: sanding shellac before sealing?
Michael Dale Payne wrote:
i lightly sand with 000 steal wool prior to appling finish. you just need a little tooth to insure good adhesion if using a waterborne.


I'd be very carful using steel wool prior to applying a waterborne finish, you could easily end up with a rust stain in the finish. Make sure you clean off any stray strands thoroughly.

I've never had any adhesion problems spraying USL over shellac and I've also sprayed 5 in a day with no troubles, roughly 2 hours apart.
Author:  James W B [ Fri Nov 20, 2009 7:45 pm ]
Post subject:  Re: sanding shellac before sealing?
Mike ,I shot 5 coats of Em 6000,not shellac.They were an hour apart,seems to be fine.
James
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