Author Topic: Sanding between coats?  (Read 634 times)

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Offline rookie08

  • Posts: 208
Sanding between coats?
« on: June 13, 2020, 09:36 PM »
I’ve got an HVLP system to paint some shelves I made.  Any suggestions an what grit(s) to use and when to sand ( between each coat? Only after primer?)

Thanks everyone!

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Offline Alex

  • Posts: 6629
Re: Sanding between coats?
« Reply #1 on: June 14, 2020, 03:00 AM »
Somewhere between 180 and 320, depending on how rough your layer of paint is. But higher is better.

I mostly sand by hand between layers, it is really easy to go through your paint with a power sander. If you have a large surface like a shelf or door it is alright to use the sander, but stay away from edges and do those by hand.

When sanding by hand, mount the paper on a block for straight pieces and use a sanding sponge for curves.

Offline xedos

  • Posts: 341
Re: Sanding between coats?
« Reply #2 on: June 14, 2020, 07:58 AM »
What do the instructions for the paint / coating you've chosen say ?

Many will specify whether to sand between coats or not.

Offline aloysius

  • Posts: 398
Re: Sanding between coats?
« Reply #3 on: June 14, 2020, 08:03 AM »
Dependent (more or less) on the substrate you're painting:  natural hardwood/softwood timbers, artificial bonded boards, veneer-faced ply etc. & the product; acrylic, oil or 2-pack lacquer, enamel, emulsion or milk paint etc.  Each variable can provide different results.

Generally the first coat (again dependent on the nature & type of finish used) will raise the "grain" considerably, & require a slightly coarser sand to remove these raised fibre ends back to a smoother substrate face.  Especially if thinned as is often recommended by finish manufacturers.

Subsequent coats will require less intensive &/or higher grit count intermediate sanding, just to denib the previous surface & provide an adequate key for the new coat.  I often use a quartered sheet of 240G for the first & 400G for subsequent coats.  I like to use the quarter folded paper sheets in my hand only, as this (possibly erroneously) allows a more intimate "feel" of the surface being denibbed.

I seem to get the best results when each surface is thoroughly not only dry but sufficiently hardened too, which is often temperature dependent & may take more than 24hrs between coats.
« Last Edit: June 14, 2020, 08:09 AM by aloysius »
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Offline tjbnwi

  • Posts: 6285
  • Cedar Tucky Indiana
Re: Sanding between coats?
« Reply #4 on: June 14, 2020, 08:04 AM »
The product we spray specs 240 between coats. Granat Net with an interface pad on 125’s or RTS’s.

For hand sanding we use 320.


Offline rst

  • Posts: 2418
Re: Sanding between coats?
« Reply #5 on: June 14, 2020, 10:02 AM »
 I've been sanding fine woodworking since 1971 and still use the same process, light coat...hand sand with 220, second coat, 320 grit, final coat.  I've used this the solvent based laquer and use the same sequence with water based finish.  Polished with Johnsons paste floor wax.
« Last Edit: June 14, 2020, 06:43 PM by rst »

Offline rookie08

  • Posts: 208
Re: Sanding between coats?
« Reply #6 on: June 19, 2020, 01:46 PM »
Great info.  Thanks everyone!