Sanding between coats of shellac

Some will possibly disagree; however, the results speak for themselves. I prefer to use 600 grit paper to sand between coats of  dewaxed shellac used to seal white oak:

Enjoying the journey.

As I have mentioned before, one key item in a finishing schedule is having the right sandpaper, like 3M’s 216U Fre-Cut™ Gold. I discussed the use of this paper in an earlier article; but I still must remember how critical it is to have the proper tools to do the job. And in finishing, this paper is an essential tool. The surface of the white oak is silk smooth after sanding. The smooth surface will telegraph into the sprayed varnish, yielding a very nice, smooth finish. Who said waterborne coatings were difficult to use?

Note: Sealing the surface of white oak and (especially) red oak is essential when using waterborne coatings. Avoid applying (typically) high-pH waterborne coatings directly on the raw wood surface of high-tannin woods like red and white oak, as pin-holing and bridging are likely to develop; that would make it difficult to get a nice, smooth finish.

Next: Attaching the top, and start spraying the varnish.

Al Navas

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Comments

    • Al Navas says

      Thanks, Todd!

      Just like you, I love to share the work I do. And when it helps others, it is much better — yes-sir!

  1. says

    Al, what kind of finishing system are you using?
    This is great information. Do you normally stick with water-based finishes? Do you have any recommendations for other washcoat material? I cannot find any dewaxed shellac up here.

    • Al Navas says

      Troy,

      I am glad you find this information helpful! And THANK-YOU FOR YOUR SERVICE TO OUR WONDERFUL COUNTRY!!!

      1. Do you normally stick with water-based finishes?

      Yes. Except for the alcohol-based shellac to seal the oaks, I switched completely to waterborne coatings. Even for walnut, for example, I use the waterborne shellac, which works great (but don’t use on the oaks). I have stuck with the Target Coatings for the last several years, and have gotten to know them quite well. I suggest to try to stick to one brand for a while, until you get familiar with the ins-and-outs. It helps to get you out of the woods in difficult-to-finish woods. And the oaks, both red and white, but in particular red oak, are quite touchy when it comes to waterborne coatings. I wrote an article a while back, showing the Target waterborne garnet shellac in use, on walnut (you will find the article at http://sandal-woodsblog.com/2010/02/23/preparing-to-finish-the-legs-for-the-stand-up-desk/ ):

      2. Do you have any recommendations for other washcoat material? I cannot find any dewaxed shellac up here.

      The washcoat should be a 1-lb strength shellac – I normally dilute 1 part Zinsser Bulls Eye 100% wax free shellac in 2 parts alcohol. If you cannot get the ready-to-go solution, your best bet is to order the dewaxed shellac flakes from the lower 48, and dissolve your own in alcohol. It is always recommended that you crush the flakes into small pieces, to enhance dissolution – and shake often. I just don’t use flakes, as the locally-available dewaxed shellac works so well. You can refer to the chart available at http://www.shellac.net/PoundCutChart.html for the dilution ratios. In fact, I wonder if you might be able to order the flakes directly from them? :)

  2. says

    Al – you wrote: “Avoid applying (typically) high-pH waterborne coatings directly on the raw wood surface of high-tannin woods like red and white oak, as pin-holing and bridging are likely to develop; that would make it difficult to get a nice, smooth finish.” I use a lot of red oak and when I stain it with a oil based stain like Minwax, stain wicks up to the surface for days afterwards. Is this what you mean by pin-holing? If not, what causes the problem I described?

    Jeff

    • Al Navas says

      Jeff,

      Pin-holing results due to the reaction between the high-pH waterborne coating and the high-tannin (acidic) woods. It is an effect analogous to improper wetting due to high surface tension of liquids, which prevents spreading of the liquid on a surface. It is also similar in its end result to contamination of the surface by silicone.

      Red oak is very, very porous and absorbs liquids only to regurgitate them later, as you have experienced. What I started doing years ago is sealing the surface with a “wash coat” of wax-free shellac. This makes it a little harder to get to the final color you might wish to get, but it also expedites the finishing process, as the stains will not penetrate very deeply. If you are unable to get the deep color you want, then you can add color to your topcoat, and slowly build up the color until it is right. When the color is added this way, it is called “toning”. I always tone using sprayed topcoats, as it gives the best control. That is how I was able to get the nice, even color on the dust cover for the desk – even though the frames are poplar and the panels are red oak. In the second photo you can see the lighter wood not yet sprayed, and the color already imparted by the toner coating:

      Dust cover in place.

      Spraying the dust cover.

  3. says

    Hi Al,

    I agree about sanding between coats of shellac. I have used 400 – 600 paper and it really makes a difference in the smoothness of the sealer coats. I sometimes use 0000 steel wool on the final coat before putting anything on top of it.

    All the best,

    Doug

    • Al Navas says

      Doug,

      Great – I am glad you find similar results. Although I have never tried 0000 steel wool on shellac, I will try it at some point. Thanks for the tip! I have used it with the solvent-based topcoats, and the results are wonderful.

      Note for the readers: Steel wool is OK to use with solvent-based coatings. However, it is a big no-no with waterborne coatings, as discoloring could take place due to reaction of the steel wool with the water.