sealing with sprayed shellac

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fergy

New User
Fergy
This is the first time I've worked with shellac, and I'm spraying it over an transtint dye that was followed with an application of wet-sanded danish oil to pop the grain and fill the pores. I let the danish oil cure for three days prior to spraying the shellac.

I'll be following the shellac with an application of sprayed pre-cat lacquer, several coats that are tinted. The shellac is serving mostly as a sealer over the danish oil, to isolate it from the lacquer. It's also serving as a sanding sealer to allow me to polish out the base layer before the lacquer is sprayed.

I am planning two coats of shellac. How much can I sand it down between coats? Can I go at it with the RO sander and a 320 pad? I'd like to smooth out the panels quite a bit. Do I need more than two coats?
 

Tarhead

Mark
Corporate Member
I would wet sand with the oil before the shellac to make a slurry grain fill; dry; spray shellac; dry; light buff w/0000 steel wool; spray the lacquer.
 

fergy

New User
Fergy
Perfect, that's what I did, though my first step was an alcohol dye. Had I been smarter, I would have used water based to get less splotching. The rest of your schedule was what I had planned.

I used a maroon sanding pad with the danish oil to create that slurry. I was amazed how much color/excess dye it pulled back up in the oil, but it did help a bit with the splotching.

I was more concerned with how many coats of shellac I should go with as a sealer, and how deep I can sand them.
 

Tarhead

Mark
Corporate Member
The shellac is not really part of the surface coat in this situation...it's just to allow bonding for the lacquer. If you sand it off you're left with an oil to lacquer bond which isn't very strong. I'm ham handed with sandpaper and get better results with steelwool.
 

fergy

New User
Fergy
Gotcha.

I need to spray a second coat of shellac as I had a couple of ripples, so I'm looking at the first coat as a scratch coat.

Having never used it, I just don't have a "gut feeling" of how much of a solid barrier it creates. It sure sprays nicely. And I'm quite pleased with the color it added, in this case. I was worried, but it really warmed up nicely.
 

Howard Acheson

New User
Howard
First, let me STRONGLY suggest you go through your whole finishing process on scrap from your project.

There is a good chance that applying a catalyzed lacquer over shellac will cause an interaction between the two. The solvents in cat lacquer are very aggressive.

As you have never used this schedule before, don't let your project be your learning experience.
 

fergy

New User
Fergy
From everything I can find, this is a perfect use for shellac, and the post-cat lacquers are supposed to be fine with it, from everything I'm reading.

But, I was planning on testing.
 
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