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When to Use Sanding Sealer
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GF sanding sealerWhat is "sanding sealer" and what's it good for? Below, Michael Dresdner offer's a short course on the properties and uses of sanding sealer to a Woodworker's Journal eZine reader:

Q. In all my years of finishing and refinishing furniture, I have never used sanding sealer. When and why should it be used, if at all? Will it make a big a difference in the end results of my projects?

A. Michael Dresdner: "Sanding sealer is never mandatory -- it is an option that saves time and material in some situations, and is unnecessary in others. Some woods, like cedar, spruce, and poplar, are so porous that they tend to suck up the first few coats of sprayed lacquer as if nothing were applied. Other woods, such as walnut and mahogany, require a good bit of sanding to level the pores even when pore filler is used. In both cases, the material of choice would be something that builds up quickly and is very easy to sand. Enter sanding sealer.

"Sanding sealer is lacquer, or some other basic coating, with zinc stearate added. The stearate, which is a soft, fluffy soap, adds loft to the lacquer, making it build up and fill in pores much faster. It also makes the lacquer softer, and acts as a lubricant when sanding, so that sanding sealer powders off quickly and easily. These characteristics make it ideal for trimming both the number of coats and the amount of time spent sanding them. This is especially helpful when you are trying to build a perfectly flat, pore-free finish. It is useless, in fact, counterproductive, for the open pore "natural" look finishes more popular today.

"A word of warning is in order. The stearates make sanding sealer rather soft. If you put a hard, brittle finish, like lacquer, over a thick, soft one, like sanding sealer, it is much more likely to chip and crack. For that reason, if you use sanding sealer, stick to one or two coats at the most, and plan to sand most of it back off. For the same reason, and because it tends to shrink as it cures, it is not advisable to use sanding sealer instead of pore filler."

From the Woodworker's Journal eZine archives

It's important to recognize that the term "sanding sealer" means different things to different wood finishers. Many people use nothing but a coat of dewaxed shellac as a sanding sealer. Zinsser SealCoat, a pre-mixed 2 lb. cut of crystal-clear dewaxed shellac, is one of the most lauded products in this category. It works great for sealing raw wood and as a barrier coat between two possibly incompatible finishes - like an oil-based stain and a waterborne top coat. It dries super-fast and sands very well.

What SealCoat doesn't do is offer lots of fast surface build. If you want a sealer that will help you stop up thirsty pores and smooth out the surface of the wood, you're better off with the stearated variety of sanding sealer mentioned above. General Finishes EF Sanding Sealer is a high quality acrylic waterborne sanding sealer that builds fast and makes sanding smooth and easy. For wood with large, open grain, such as walnut or mahogany, sanding sealer is especially handy as a final fill after most of the grain has been evened out with grain filler. Now, what is "grain filler" and what's it good for? See "Using Wood Grain Filler" here on the Rockler Blog.

posted on March 23, 2007 by Rockler
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15 thoughts on “When to Use Sanding Sealer”

  • Tim

    great tip & post. i'm still kind of new at this, so that helps!

  • Bill

    This is an excellent article. I need to refinish a cedar entry door
    that has stress marks and an old coat of lacquer (it is at least 80
    years old. Now I will just sand and refinish it. Thank you

  • Don Lewis

    I am constructing a number of large picture frames made with raw basswood. Some frames will be painted and some will be stained. Basswood fuzzes up with sanding, so should I use a sanding sealer like Zinsser Sealcoat and if so, how many coats? For the stained frames, should I use a seal coat and a stain per-conditioner or is there some incompatibility?

  • [...] When to Use Sanding Sealer. [...]

  • Loren

    I was introduced to sanding sealer, by another carpenter friend of mine when i was doing extremely intricate scroll saw fretwork with birds, vines, leaves and berries. I coated the plank before doing the scroll work. It was amazing. It not only helped keep the tiny pieces from breaking off, but it made sanding so easy and the finished wood was super smooth. It turned out fantastic. But what about using sanding sealer over a piece that will be stained, but you don't want it to soak up too much stain. Will the stain still work. ?? I guess i need to use oil-based sealer with oil-based stain??

  • mark gasser

    I put a light coat of Zinsser universal sanding sealer on some cedar and let it dry overnight. next day I tried to sand a small run but it was gummy and clogged the open coat sandpaper. the lot # is S30107 D. does anyone know if this can is too old? I don't know how to read the date of manufacture. this stuff is supposed to sand easily. thank you.mark

  • Linda Cary

    I used the sanding sealer in my garage on shelves. The next day there were lots of spots of globbing from "drips". I thought I had smoothed out the excess well but apparently not. Now I need to apply my lacquer but when I try to sand those globs, lose stain along with everything else. How can I get these globs off without stripping the stain?

  • Tommy

    Ok, thank you very much for this, i didn't understand the until not about wood filler & wood grain filler, all the hardware stores near me only sell various types of wood filler. thanks again!

  • Roy Holmes

    If I use sanding sealer or shellac prior to polyurethane or lacquer, will it prevent future cracks or splits?

  • Karen Howard

    I sand and woodburn cigar boxes. I never know what kind of wood I'll find until I've sanded the box. What kind of sealer should I be using?
    I've tried polyurethane, but it's toxic and I try to shy away from toxins for my customers' sake (and my own).
    I've tried high gloss "triple thick sealer", which advertises itself as safer than toxic sealers. The problem with that is, if I don't use it all up quickly, it turns too thick to use.
    I'm now using shellac, but have to use up to 3 coats before the box looks finished.
    Any suggestions?

  • Fred Newton

    Thanks for this great article!...I do a lot of wood lure making, and found this article very helpful ! Will go look for your article on grain filler....can use some guidance here!

  • Eugene de Beer

    I would like to know if I can use Sanding Sealer as a final finish alone on kitchen cupboards?

  • pat carlson

    what do you recommend for sanding sealer with
    balsa wood and RC model airplanes ?

  • Horace Sutterer

    Bulls Eye Seal Coat is excellent for bringing out the true color of wood before you do anything else to the wood. Oh, it makes natural colors so vibrant it'll amaze you! I use it on all the wood I use to make my footballs then I seal them with clear epoxy.

  • Peter

    Can I use cellulose or polyeurethane varnish or oil on top of sanding sealer

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