Finish Coating Toughness Comparisons

      This discussion about how to choose a tough finish includes a brief explanation of the industry TR standard rating system. March 29, 2006

Question
I am refinishing a table top that is used everyday. The customer is sold on polyurethane because of its inherent toughness and water resistance. I like working with lacquer because of the ease and quick drying, and I'm set up for lacquer. Is there a lacquer out there that has properties similar to polyurethane?

Forum Responses
(Finishing Forum)
From contributor A:
Sherwin Williams makes a pre-cat lacquer that I use on projects with good success. It is available only in 5 gallon quantities. I made a table for our own use and sprayed a couple coats of their pre-cat lacquer (medium rub) and have been pleased with its wear. Several months later with a raking light you can see only very slight scratching - and our table gets very hard use.



From contributor B:
I would go with a good quality post cat lacquer. It is almost CV strength without problems and it will be much stronger than polyurethane.


From contributor C:
Why not just give the customer what she wants and use polyurethane? It's no more difficult.


From contributor D:
Your customer is right about polyurethane. It is a TR 5 coating as the others are TR3 at best. This is the reason why they are asking for this product. The bottom line is this, there is no product in lacquer form or conversion varnish form that will hold up as well as polyurethane. The only product that's more durable is polyester and this product is rated as a TR7 coating.


From contributor B:
The TR finishing standards are used to group finishing products into classes, by solvent, solids, and VOC. Just because something is a higher TR # doesn't mean it is a stronger finish.

TR-0 Synthetic and Penetrating Oil is a minimal system offering minimal wood protection and must be renewed often.

TR-1/OP-1 Standard Lacquer contains the least amount of solids and the greatest amount of solvents. This finishing system is being phased out in many parts of the country because of its high volatile organic compound (VOC) content.

TR-2/OP-2 Catalyzed Lacquer contains less solvent and more solids, and is acceptable in certain areas of the country under the existing air pollution standards. It is more durable than standard lacquers, and is widely used in the cabinet industry.

TR-3/OP-3 Water Reducible Lacquers contain fewer organic chemicals, and are not in general air pollutants. However, the clarity of water-reduced finishes is sometimes less than that of solvent-based finishing systems. This in part is caused by microfoam which develops in the water-based finishes.

TR-4/OP-4 Conversion Varnish is a higher solids varnish used by the kitchen cabinet industry. It is durable, easily repaired, yet not as clear as lacquer or vinyl.

TR-5/OP-5 Catalyzed Vinyl is the first group of finishes which has more than 50 percent solids at the spray gun and it meets most states' environmental requirements. It may be sprayed in both light and heavy coatings and is very durable, resistant and clear.

TR-6/OP-6 Catalyzed Polyurethane is an extremely durable, clear finish. It is used on hospital casework and doors, and may be rubbed to a high gloss finish.

TR-7/OP-7 Polyester is the densest and hardest of the coatings, but it may fracture and crack if it is damaged.

OP-8 Polyester/Polyurethane is a combination finish which is used mainly in production industry. It is more elastic than polyester, extremely resistant, clear and durable.

The TR standards set guidelines for each type of finishing products and to be in compliance makes life easier for the finish companies. I would put the TR 4 C/V I use against most polyurethanes and it will out perform them in every category. We also use a post cat lacquer that would do the same. We have tested them and there is little comparison. We have used some catalyzed polyurethane that is extremely strong but not worth the effort.



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