Sanding before Priming

I was curious as to how much sanding is usually necessary before priming.
Is it normal to sand old or even relatively new paint completely off before priming, or just enough so that the primer adheres?
I ask because I'm restoring some old artwork on a plywood cabinet, and if I don't sand it off completely it would be easier to restore the art by masking and going over it with each of the three or four colors originally used rather than to have to start from scratch.
The artwork was originally done in lacquer paint, however the paint I'm using to restore it is latex.
Thanks.
Darren Harris Staten Island, New York.
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On Sat, 1 Dec 2012 21:34:47 -0800 (PST), snipped-for-privacy@mail.con.com wrote:

don't sand it off completely it would be easier to restore the art by masking and going over it with each of the three or four colors originally used rather than to have to start from scratch.

You want to take off enough to get a smooth coat of primer. It does not have to be bare wood.
Paining over lacquer with latex is just repainting, not restoration.
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On Sat, 1 Dec 2012 21:34:47 -0800 (PST), snipped-for-privacy@mail.con.com wrote:

Just enough to give it tooth for the primer to adhere, unless there is paint flaking off. I'd sand all the flaky paint down and off the cabinet. Sanding is usually done to flatten the piece for painting. The glossier the paint, the flatter it has to be without showing the blemishes.

don't sand it off completely it would be easier to restore the art by masking and going over it with each of the three or four colors originally used rather than to have to start from scratch.

Lacquer is much, much thinner than latex, so you'll have lines at the edges. Those can be sanded flatter (with a dual-action sander, or DA) once the latex hardens completely. Then you can put a clear covercoat over it all for a better look. I doubt you'll be able to match the colors and glosses, so plan on painting the entire panel once you start. Paint usually won't stick well to vinyl, either, so I'd avoid that.
-- Happiness lies in the joy of achievement and the thrill of creative effort. -- Franklin D. Roosevelt
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On 12/1/12 11:34 PM, snipped-for-privacy@mail.con.com wrote:

If whatever you're applying on top will stick to what's beneath it, you don't need to sand down to wood. With many woods, whatever is already on the surface is better to paint over than bare wood, anyway.
Smooth is relative with paint, as well. I can't tell you how many times I've sanded a drywall patch "perfectly smooth" only to see the borders after painting. If there's any texture or artwork on top, it often hides those imperfections. But a single color, smooth topcoat will often show them.
The solution might be building up a couple layers of primer with flat sanding in between coats. Good auto-body guys are maters of this.
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On Sunday, December 2, 2012 12:50:47 AM UTC-5, Ed Pawlowski wrote:

I'm not sure what you mean by that. As long as the surface is smooth the three different color matched latex paints I have, which are actually primer and paint in one, will be used on the entire side which was actually originally stenciled and sprayed. The base/background color, the second and then third color, followed lastly by the black outlines.
In fact, the most difficult part is the black outlines, which is really all I need to get right.
On Sunday, December 2, 2012 6:59:47 AM UTC-5, Mike Marlow wrote:

Ok. I'm not 100 sure what you mean by "unfeathered edges". Is that were two different colors meet? I will obviously be using brushes. Foam for the main colors and a thick liner brush for the black outlines.
On Sunday, December 2, 2012 9:11:10 AM UTC-5, Larry Jaques wrote:

Ok. There is no vinyl involved in this project.
The paint I'm using is Valspar Interior Semi-Gloss, which is a paint and primer in one. I did ask for something to clear coat it with and was directed to get Valspar Clear Gloss Premium Enamel in a rattle can, which is supposed to seal and increase durability.
On Sunday, December 2, 2012 1:08:17 PM UTC-5, -MIKE- wrote:

In a question involving a different but similar project, *priming* over a clean, lightly sanded surface that still has paint is no problem, correct?

I don't want to lose the original artwork completely, since it will be my guide when re-painting.
But as far as sanding *after* I finish re-painting. Camn this be done without having to worry about bleed over?
Thanks a lot.
Darren Harris Staten Island, New York.
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On Sun, 2 Dec 2012 12:33:34 -0800 (PST), snipped-for-privacy@mail.con.com wrote:

different color matched latex paints I have, which are actually primer and paint in one, will be used on the entire side which was actually originally stenciled and sprayed. The base/background color, the second and then third color, followed lastly by the black outlines.

When you "restore" something, you bring it back to original condition. If you have a '55 Chevy and replace the chrome on the bumper with silver paint, it is just painted, not restored. Replacing lacquer with latex is not a restoration.
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I still don't see the parallel. I'll be using latex and a clear gloss over that for protection. Many other have done this in restoring their cabinets and the resulting artwork looks factory new.
Darren Harris Staten Island, New York.
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On 12/2/12 2:33 PM, snipped-for-privacy@mail.con.com wrote:

Not that I know of. Priming over a surface that has different, contracting colors can help keep the top color even.

I don't know what "bleed over" means, and I'm certainly no paint expert. But I would never sand the final, finish coat of paint. Maybe some do.
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On Sunday, December 2, 2012 6:34:51 PM UTC-5, -MIKE- wrote:

I used a foam roller. One coat with horizontal strokes, the second with vertical strokes and the third with horizontal strokes again, and I can still couldn't completely get rid of the "parquet-like" pattern. So I hope when it is painted over it will look ok.

I'll be force to use brushes at certain points and assume I'll have to deal with some streaks as a result, so I was thinking a light sanding might help. (Someone even mentioned using #000 steel wool to "feather" any slight raises).
Thanks.
Darren Harris Staten Island, New York.
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The original paint was lacquer and therefore somewhat transparent. If you sand it too much the color underneath the color you are sanding stars to come through. It doesn't chip, so there are no unfeathered edges to worry about.

When one color contaminates an adjoining color.
Darren Harris Staten Island, New York.
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On Dec 2, 12:34am, snipped-for-privacy@mail.con.com wrote:

Only two things will stick reliably to cured lacquer -- lacquer or shellac. Clean, scuff with 220 until no longer glossy. Seal with clear dewaxed shellac (Seal Coat), scuff when dry, and paint with whatever you like. The shellac will also seal the masking tape edges to create sharper lines and prevent paint from seeping under.
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