You’ve heard of wet sanding, and you’ve always wondered: when are you suppose to wet sand, and when are you suppose to dry sand? What’s the difference between the two?
Wet sanding, which is sanding with the addition of water to act as a lubricant, is less abrasive than dry sanding, and results in a smoother finish. It’s best to wet-sand the final finish of a project. Dry sanding removes more material, and smooths rough material quickly.
There are a lot more details, though, so lets dive in!
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Wet Sanding Vs Dry Sanding: What’s the Difference?
|Wet Sanding||Dry Sanding|
|Removes less material||Removes more material|
|Uses lubricant (usually water)||No lubricant required|
|Reduces mess||Significant mess|
|Takes more time||Takes less time|
|Uses higher grit sandpaper||Uses lower grit sandpaper|
|Produces super smooth finish||Produces smooth finish|
|Done by hand||Done by hand or with power tool|
At a glance, wet sanding and dry sanding do basically the same thing – they both remove material to create a smoother surface.
But the surface created by wet sanding is even smoother than the surface created by dry sanding, however, it takes significantly more time to do.
There are other differences as well. Wet sanding uses water, dry sanding doesn’t. Wet sanding is less messy. Dry sanding is frequently done with power tools.
But the primary difference, the reason you’d choose one method over the other, is the relative smoothness of the result produced.
When Should You Wet Sand?
It’s best to wet sand when you’re looking for a super smooth finish, or when sanding is going to create a huge mess, and you’re willing to spend a long time sanding to avoid that.
If you have a lot of material to remove, then dry sanding is probably a better choice.
From a woodworking perspective (my specialty) it really makes the most sense to wet sand at the end of a project, after you’ve already applied the finish and want to smooth out any brushstrokes or dust nibs.
It doesn’t make sense to wet sand bare wood, for a couple of reasons. First off, you don’t want a super smooth finish yet; fine sawdust clogs wood pores, and makes wood more difficult to stain.
Secondly, wood is sanded in order to remove manufacturing marks or flaws in the wood. To do this, you’re going to need to take off a fair amount of wood. It would take forever to do that while wet sanding.
But wet sanding is great for smoothing out the final coat of wood finish!
Different Materials: Should You Wet Sand or Dry Sand?
Whether you choose to wet sand or dry sand also depends on the materials you’re working with. We’ve talked a bit about wood already, but here are some other materials that are frequently sanded.
Should You Wet Sand Drywall?
Drywall can be wet sanded, and that results in much less of a mess than dry sanding, as well as a smoother surface. However, because drywall typically covers a large space, wet sanding drywall requires a much larger time commitment than dry sanding.
I’ll be honest – the few times I’ve sanded drywall, I’ve opted to dry sand it. But if you’re really picky about the smoothness of your walls, it might be worth wet sanding.
Can You Wet Sand Primer?
Whether you wet sand primer or not depends entirely on what type of primer you’re sanding. For latex paint primer (water, oil or shellac-based,) you don’t need to wet sand, since the layer of paint will cover that perfectly smooth surface anyway. Auto-body primer, on the other hand, should be wet sanded.
Should You Wet or Dry Sand Tile?
If you’re prepping masonry, porcelain or ceramic for painting, you should definitely wet sand – these materials require as smooth as a surface as possible.
I can’t think of any other reason you’d be sanding these things, but even then, you’d probably want to wet sand!
How to Wet Sand
Step 1: Get the Right Sandpaper
A lot of people wonder if you need special sandpaper for wet sanding. The answer? Maybe.
Wet-dry sandpaper can be used for both wet sanding and dry sanding. Otherwise, you’ll need wet sandpaper for wet sanding and dry sandpaper for dry sanding.
I usually use wet-dry sandpaper, because I don’t wet sand frequently enough to purchase sandpaper that’s designed for wet sanding alone.
Wet sanding requires higher grit sandpaper than dry sanding does, so instead of starting with 80 grit like I would for dry sanding, I usually start with 400 grit and work my way up.
Step 2: Mix the Lubricant
Mix some water and a few drops of dish detergent in a medium-sized container. The dish detergent makes the water a little slipperier, making it an even better liquid for the sandpaper.
If you’re working with wood, yes, you could also use mineral spirits. But, I’m not sure why you’d want to. Mineral spirits cost money, and water is free. There’s no advantage to mineral spirits – your wood is already finished, so you don’t have to worry about damaging the wood with water.
Step 3: Sand
Dip your sandpaper in the water mixture, and wrap it around a wooden block. Hand sand the wood in an ovular shape, with the longer sides of your oval going with the grain.
As the sandpaper dries out, dip it back in the water mixture. If there’s any buildup of wet “sawdust” (really finish dust, in this case,) wipe the piece down with a rag to clean everything off.
You’ll notice that I specified that you should hand sand here. I wouldn’t recommend wet sanding with an orbital sander. First off, these are electrical tools, and getting them wet generally isn’t a great idea.
Secondly, the goal here is for a super smooth finish. Orbital sanders are more aggressive than you need.
Step 4: Repeat
Repeat the process with gradually greater grits (800, 1500, 2000) until you’ve reached 2000 grit sandpaper.
Step 5: Buff
Grab some furniture wax, and buff the piece down with a soft rag. Enjoy your flawless finish!
How to Dry Sand
I have an entire post devoted to dry sanding wood, but I’ll provide a quick summary below!
Step 1: Sand With the Lowest Grit Sandpaper
Grab the lowest grit sandpaper you plan to sand with (check out this post if you’re not sure what that is,) and rub the sandpaper on the wood in the direction of the grain.
Once again, if you’re hand sanding, wrap your sandpaper around a block of wood to make it easier to work with.
For the record, you can use an orbital sander for dry sanding, and if you’re sanding a flat surface, the sander will probably make things significantly easier. I have this sander, and absolutely love it!
Generally, you should sand with the lowest grit sandpaper until you can’t see any more dents or marks from the manufacturing process. For more details on how long you actually need to sand for, check out this post!
Step 2: Remove Sawdust
Before you move onto the next grit sandpaper, you’ll want to get all the sawdust off your piece. Otherwise, the dust from the lower grit paper will get trapped between the new sandpaper and the piece, creating large scratches in the wood that are hard to get rid of.
I usually use a shop vac to vacuum up the dust, but a rag or compressed air work too!
There are a couple of ways to remove sawdust. I like using a shop vac and vacuuming up the dust.
Step 3: Repeat with the Next Grit
Repeat steps 1, and 2 with the next grit sandpaper. I usually go in this order: 60, 80, 120, 180. There are some skipped grits in there, but I find it doesn’t make too much of a difference (and I usually don’t have those other grits in stock.)
For the most part, I don’t sand past 180 grit because that starts to close the wood pores, which blocks stain from soaking into the wood.
Repeat this until you’ve hit every sandpaper up to 180 grit.