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Hi all -

I am getting ready to stain and paint part of a furniture piece I am working on and have a few questions related to sanding. Part of the dresser I will sand, stain and poly. Other part of the dresser I will sand, prime, latex paint and possibly poly.

Sanding between poly coats (on top of stain):
  1. It is my understanding we sand between poly coats, correct?
  2. If so is it a very gentle sanding? What grit?
  3. How many layers of poly do you recommend?
Poly over Latex Paint:
  1. Can I apply poly over latex paint?
  2. Is it recommended?
  3. Do I still sand between poly coats if I apply poly over paint? If so, same grain as above?
Sandable Primer on wood, under Latex Paint:
There are several imperfections in the wood of this furniture piece, but there are also molding. This is the part of the dresser I am not staining, but painting. To get a nice smooth finish, -
  1. Do you recommend a sandable primer before the latex to fill the imperfections? (I am using wood filler to fill most of the holes)
  2. Will a sandable primer make it hard to smooth out the molding?
I appreciate all the help.
 

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I use mineral spirits-based poly. I spray 3 coats, 2 coats of gloss and a topcoat of satin, sanding the first two with 320 or 400 grit wet or dry sandpaper using mineral spirits as a lubricant. It takes me that many coats to build a thick enough film that I can polish it to the sheen I like. When the poly is thinned so it atomizes well, only a very thin coat will hang on vertical surfaces without sagging. The water based poly seems thicker to me, so it may build faster.

I like the eggshell finish you can get with polyurethane over enamel paint. Again, I use spirit based finishes. The only way I know to be sure of compatibility is to do a test. The clear coat will accentuate any imperfection in the paint finish below it. Once the clear coat is applied, you can't do anything about this. If you scuff or sand the paint in any way, the scratch pattern has to be perfectly uniform. I prefer scotch brite abrasive over sandpaper for this.

I work this the other way also, using thinned poly as a primer under enamel paint. Porous materials like MDF or LSL will soak up a ton of it and sand very smooth. Trying this with water based material sounds to me like it is worth a try.
 

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Hi all -

I am getting ready to stain and paint part of a furniture piece I am working on and have a few questions related to sanding. Part of the dresser I will sand, stain and poly. Other part of the dresser I will sand, prime, latex paint and possibly poly.

Sanding between poly coats (on top of stain):
  1. It is my understanding we sand between poly coats, correct?
  2. If so is it a very gentle sanding? What grit?
  3. How many layers of poly do you recommend?
Poly over Latex Paint:
  1. Can I apply poly over latex paint?
  2. Is it recommended?
  3. Do I still sand between poly coats if I apply poly over paint? If so, same grain as above?
Sandable Primer on wood, under Latex Paint:
There are several imperfections in the wood of this furniture piece, but there are also molding. This is the part of the dresser I am not staining, but painting. To get a nice smooth finish, -
  1. Do you recommend a sandable primer before the latex to fill the imperfections? (I am using wood filler to fill most of the holes)
  2. Will a sandable primer make it hard to smooth out the molding?
I appreciate all the help.
You can use a waterborne poly over latex paint. In fact you would be better off since an oil based poly tends to yellow with age and that yellowing would alter the color of the paint.

When ever you put any finish on wood it raises the grain and makes the surface fuzzy. The fuzz is suspended in the finish and sanding between coats smooths the surface. It doesn't take a great deal of sanding but should be done with most finishes. The scratches made by sanding aids the adhesion of the finish. Some finishes like shellac and lacquer literally melt into the dried finish so if the surface is smooth sanding could be skipped. When sanding poly use a sandpaper 180 grit or finer. If you thin the varnish then use finer grit. If a finish is very thin the scratches done by between the coats sanding can show in the finish. In most cases the scratches are covered up with the coat of finish.

Sandable primer really aids the smoothness of paint. It levels the surface better than anything you could use. Just be sure the primer is compatible with the paint. Rattle can primer in most cases isn't compatible with latex paint. Most of it is only compatible with either oil based or automotive coatings. It would be like putting latex paint over oil based paint. It would eventually peal off and would need to be stripped to fix.
 

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When I spray over paint I use and alkyd paint such as BM Advance. I have topcoated it with waterborne urethane such as Target Coatings EM 9300 with excellent results. My sanding varies with the finish I am using. Generally though, I sand down to 220, blow the piece off with air, then wipe it down with a lint free rag, misting the rage with 50/50 water and Denatured alcohol to minimize grain raising. I then shoot two coats with no sanding between. When dry I wipe the piece, enough to remove the nibs, with 220. I then shoot another coat, let dry, wipe with 320. I finish by shooting two final coats. With heavy bodied finishes, such as paint. I shoot 1 coat, wipe with 220, then shoot two final coats.
 
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