Which finish to use?

      Various options for topcoats, and what specific problems each can help to solve. March 20, 2001

Q.
I was using lacquer on my cabinets, but it left dry spots in the finish. I switched to conversion varnish and I like the way it goes on, but I can't stand the smell. What are you using in your shops? I am thinking about trying polyurethane.

Forum Responses
Dry spots? Use sealer first, and two coats of lacquer. We use Precat lacquer and conversion varnish, depending on the job. Poly will not smell pleasant either. Your finishing area or room should be closed off from the shop, with good exhaust. If you smell it through your respirator, you're not using the right one or it doesn't fit properly. We have tried water-based product but were not happy with the end result, so switched back. But the water based smell was tolerable (you'll still need a mask).



If your ventilation is working properly, you should not be able to smell much of anything. You may try some different brands, as some companies use a vanilla scent to mask the formaldehyde fumes. As I understand it, the fumes you are smelling are a reaction between the acid and the formaldehyde. We used Sherwin Williams and it wasnít that bad at all (vanilla scent).

Conversion varnish is quite simply the best finish on the market for cabinets. Itís relatively easy to apply, easy to use, and for the buck itís a darn good finish. Lacquer canít touch it as far as durability.



Conversion is a very good finish. I use the Sherwin Williams when we want a tough, durable, premium finish. But I don't know that I would call it easy to apply--it's a bit touchy, especially for beginners. For general shop use the standard nitrocellulose is a lot easier for beginners to use, although you need to use the sealer first, of course.


I use SW catalyzed lacquer. While it isn't quite as durable as conversion varnish, it is easy to use and pretty forgiving. I use the 24% solids vinyl sealer with 3% catalyst, and two topcoats. I spray it with a pressure pot and a Graco HVLP.


I use a post cat lacquer. I find it the most durable. I cut it 20% to spray in an HVLP gun or 10% in a pressure pot. I never really liked the varnish finish.


I have had reasonably good success with SW KemAquaLac (water based lacquer). It is perhaps slightly less clear than nitrocellulose, but it dries at least as fast, sands easily and the smell is not at all bad. An added advantage is that humidity is not nearly as bad a problem as with solvent based product.


SW Kemvar conversion varnish is not at all difficult. In fact, it reduces many temperature and humidity problems. One thing to mention is a pin-holing/gassing-off problem that occurs in hot weather.

Proper catalyst ratio, 3.8 oz per gallon and adequate reduction allow for a fast setting, durable, clear finish that holds a sheen. This finish is forgiving in that it levels out well during drying.

We start with SW vinyl lacquer sealer straight out of the can, except we catalyze with super catalyst--optional. This helps hardness and sanding. Sand the sealer with 320 or steel wool.

We usually reduce the water white conversion varnish to about 15.5 seconds with a Zahn #2 cup. That is equivalent to about 33% with xylol or high flash naptha for more flow out. ButylCellosolve can also be added. This will help flow out as well, but will slow drying, so use sparingly. There are some commercial solvents available that improve flow out.

You get a lot more depth by adding additional coats.

The amber version of SW conversion varnish works well when a non-yellowing finish isn't necessary. It has more solids, costs a little more, but goes further. You can even get pigmented conversion varnish. We have had good success with these.



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