Professionals and Amateurs Together

Sanding Sealer


Modern finishing books suggest thinned shellac or Zinsser sanding sealer (a shellac with preservative). However, old books mention using a very dilute hide glue solution (like 2 ounces hide flakes per quart of water). What are the pros and cons of these two coatings as a sealer for a complicated finish like Stickley’s. Is one preferred for close grain versus porous woods? Aren’t both compatible with subsequent water or oil based finishes? What sealer coating was used around 1900 to 1920?—Dave Michaels


Bruce Hamilton replies: Shellac has the smallest molecules of all the popular finish materials used today. Because of this it penetrates deeper into the wood fibers which make the fibers appear to shimmer as light reflects off at different angles. Hide glue with its large molecules will lie on the surface and muddy the reflectivity of the wood fibers. It can, however, be use to control the porosity of wood, for example on end grain, when staining with a pigmented stain and where clarity is not important.

I use only shellac as a sealer. It is sometimes referred to as a sanding sealer but that description is not entirely correct. It does raise and freeze the wood fibers which make it easier to sand the surface of wood smooth but there are no stearates in shellac like there is in what we usually think as traditional sanding sealer. Zinsser has a product called SealCoat that doesn’t contain the wax that shellac usually does naturally. Wax can cause adhesion problems. SealCoat is also the blondest in color of all the ready available shellacs on the market. A product call Zinsser Clear shellac has no color because it has been bleached. This product has a limited shelf life and should be avoided in my opinion. Home Depot carries SealCoat and I would think Lowes would also.

Shellac is easy to use. It dries fast and has good adhesion. Top coating it only requires a light sanding to scuff it if you are using ploy or a water base finishes on top of it. Lacquer will readily melt into the shellac giving reliable adhesion.

There is some controversy when referring to Stickley finishes as to exactly how they were achieved. The formulations changed over time and also with who the manufacturer was. I have very little experience in this area. I have read George Frank’s book where he refers to using ammonia to flume the bare oak to achieve the color. This eliminated the problem of the varying porosity of the wood so the color was achieved evenly on all the wood surfaces. Some say that no shellac was used. Some say it was. Others say that wax was used. These approaches do complicate the finishing process and retard the speed of manufacturing. I think Stickley or any other manufacturer of this type and color of similar furniture would have avoided a complicated finishing process.

Finishes on furniture in the first two decades of the twentieth century were exclusively shellac. Lacquer, also known as nitro cellulose, did not come into play until the twenties when it revolutionized the way furniture could be designed and finished. It was fast drying as well as dried hard for polishing. It gave excellent adhesion throughout numerous coats applied. It readily lent itself to toning (putting color in the lacquer) and glazing which was a process of applying pigment colorings which were brushed on and then feathered off with a dry brush to accent carving and mouldings. Lacquer sprayed and dried very well over this coloring technique.

Tags: Finishing