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QUESTION:

I work at a small stripping refinishing business. We use precatalyzed sealer and topcoat. We also use an oil-based spray stain that is reduced 10 percent with lacquer thinner. After drying two days, the sealer does not sand well with 220-grit sandpaper. The sandpaper does not last very long, and the nibs from the fiber raise appear with the stain color in the nibs. The finished product looks good, but the process is very labor intensive. What are we doing wrong?

P.S. We have problems sanding through the stain and have to do touch-ups before applying the topcoat.

ANSWER:

There are several specifics about your problem that you did not mention in your question, so I can only assume what may be causing your problems.

As a first step, make sure your substrate is sanded smooth with a high-quality abrasive material — finishing up with a minimum of 180 grit and no more than 220 grit. Second, your oil-based spray stain may be something you need to consider changing. If your current material is truly an oil-based type of stain, it should not be used under the lacquer as a spray — no-wipe — stain.

In your question, you mentioned that you spray your stain on, but did not mention if you wipe the stain back off again. If not, you will be leaving the oil binder that is in the stain on the surface which will take a very long time to dry and will potentially affect the curing of the precatalyzed lacquer sealer. This may also cause the lacquer to sand poorly and load onto the paper instead of powdering freely as it normally would. Also you will have more problems with sanding through the stain in the sealer-sanding process. There are many high-quality spray-to-color stains that are available from the vendor who supplies you with your pre-cat lacquer. You may also try using some dye stains to keep the stain color clean and get more penetration into the substrate.

Lastly, you may want to try using a lacquer that is either catalyzed by your distributor or is post-catalyzed when you are ready to spray the product. These products will allow you to sand more quickly, provide a better build, and, in the end, may reduce the labor intensity of your process because of ease sanding and reducing the number of clear coats.

Ed. note: Phil Stevenson is the founder of the American Wood Finishing Institute (AWFI) in Vineland, N.J.