Why Seal Wood Before Staining

Learn the right way to seal wood in Jim Hingst's article to avoid a blotchy appearance when staining wood...

When staining wood, the results are often unpredictable. A common problem is a blotchy finish. Blotchiness refers to an uneven appearance, in which some areas of the wood are darker than others. See the photo below.

Blotchiness occurs because the wood absorbs the stain inconsistently. Where the wood fibers are loosely packed, the surface soaks up the stain more than in areas where the fibers are more densely packed. The problem of blotchiness is more common when staining soft woods, such as pine, maple and birch, which are very porous, than with hardwoods, such as oak.

To produce a more consistent finish and prevent undesirable results, you can treat the wood prior to staining. Some woodworkers will apply a pre-stain wood conditioner to fill in the pores of the wood.

In my article, Staining and Varnishing, I suggest sealing the surface with thinned varnish. The more traditional way is to apply a thinned coating of shellac. Many people prefer shellac to varnish for sealing, because it dries much faster.

Prior to staining the carving pictured above was sealed.

When sealing with shellac, use either a 1-pound cut or 1/2-pound cut. To mix your own shellac from dry flakes follow the directions in my story Making Dewaxed Shellac From Flakes.  Or you can buy a can of commercial dewaxed shellac and thin it with denatured alcohol.

For those, who decide to use shellac in a can, thin it with denatured alcohol. Canned shellac is typically a 2-pound cut, so you will need to thin it at a 1:1 ratio (in other words, one part alcohol to one part shellac).  Some woodworkers thin the shellac even more at two parts alcohol to one part shellac. This will give you a 1/2-pound cut. 

The thinner shellac will allow the wood to absorb more of the stain. If you use the shellac straight from the can without thinning it, it will over seal the surface and prevent the stain from coloring the wood sufficiently.

Test, Don’t Guess. Prior to staining your project, I advise you to test the shellac and stain on the same type of wood that you will finish.

As an alternative to using shellac, you can also seal your
carving using a 50/50 mixture of polyurethane varnish
and mineral spirits.

Sealing Procedure Using Shellac.

Apply the thinned shellac onto the surface of the wood. You can use either a bristle brush or a foam brush or you can wipe it on with a lint-free cotton rag. After you apply the shellac, use a clean rag to wipe off the excess, before it dries. Work fast because shellac dries really fast.

The end grain of the board can be problematic, because it can suck up the stain like a sponge.  It will always appear darker. Instead of using shellac, some people lightly coat the ends of a board with varnish. 

After the shellac dries in about a half hour, you can scuff up the surface with a Scotch-Brite pad or lightly sand it with 220-grit sandpaper. Scuff or sand the sealed surface with the grain. Then wipe the surface off with a tack rag.

Wait at least two hours before staining. If you varnished the end grain, you will have to wait at least a day for it to dry. After applying the stain to the sealed wood, wait about 15 minutes, before wiping off the excess. In some cases the stain may be too light for your liking. If this is the case, you will need to repeat the staining procedure. Or you may consider using a gel stain for your project, which is more opaque, if the desired effect is a darker finish.

If you follow my procedure for sealing with shellac before staining, you will produce a more uniform finish for your wood projects and avoid blotching. See the photo below.

24 hours after staining, the wood should be dry enough for varnishing. Remember that staining and varnishing is not suitable for outdoor signage projects. For exterior applications, most wood surfaces should be painted, if you expect to achieve long-term durability.

RELATED ARTICLES

Differences Between Stains and Dyes

Staining and Varnishing

Making Dewaxed Shellac from Flakes

Using Gel Stains

About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.

© 2015 Jim Hingst