Pre-catalyzed and post-catalyzed lacquer

Overview

A catalyzed lacquer is a nitrocellulose-type spray lacquer with a catalyst system that makes it harder and more resistant than ordinary Nitrocellulose lacquer. In a pre-cat the catalyst is already in the can; a post-cat has a separate catalyst you measure in before use. Furniture and cabinet shops choose them for a harder film without the cure-time fuss of a full Conversion varnish.

Pros

• Greater durability than regular nitrocellulose lacquer, according to Mohawk (manufacturer claim) and Wikipedia ("harder than standard lacquer", "excellent general furniture finish").
• Wikipedia lists good protection against wet and dry heat and says it meets UK and European standards for "general use".
• Pre-cat needs no mixing and keeps the shelf life of a normal lacquer (Mohawk quotes 12 months).
• Fast: Mohawk's Versalac post-cat is dust-free in 30 minutes and sandable in 60.
• Mohawk sells KCMA-passing versions (the maker's claim) for kitchen cabinets.

Cons

• Wikipedia notes it becomes non-reversible after about 5 days, so spot repair is harder than with plain lacquer.
• Needs spray equipment and a booth; solvents are toxic and flammable.
• Post-cat has a limited pot life: Versalac's data sheet gives 6 months catalyzed, using 6 oz of catalyst per 5 gallons.
• Mohawk says Versalac must be sanded immediately before recoating.
• Mohawk's DuraCoat pre-cat is listed at 707.95 g/L, and Mohawk sells a separate 550 VOC version; local rules vary, so check yours.

Suitability

Good for casework, kitchen cabinets, and tables in interior use, on Red oak, White oak, Hard maple, Hickory and Pecan, after filling pores if wanted (Grain filler (pore filler)). Not for outdoor work. If you need a harder finish than this, the alternatives are Conversion varnish and Catalyzed polyurethane (2K).

Coats and application

Prepare as for lacquer (Sanding schedule, then Sanding sealer (and vinyl sealer) or Dewaxed shellac). Spray (Spraying with HVLP) two or three coats. Mohawk's Versalac sheet allows reduction with lacquer thinner up to 20%; the DuraCoat sheet limits total film to 4 dry mils. Example: sealer, 320 sand, two coats of Versalac an hour apart, sanding lightly before the second, then wait several days before rubbing out (Rubbing out a finish). Always follow the can's mix ratio; a post-cat batch should be used within its pot life.

Compatibility

• Goes over Sanding sealer (and vinyl sealer) made for lacquer, over dewaxed shellac, and over dry dye and pigment stains (Alcohol and oil-soluble dye stain).
• Do not mix lines: use the catalyst number printed for the exact product (Versalac's is a specific part number in the data sheet).
• See Finishing sheet goods (plywood, MDF, MDO) for veneered panels.
• Not for use under or over Water-based lacquer without a test.

Care and repair

Wipe clean with a damp cloth. Scratches in the surface can be rubbed out once cured; deeper damage is repaired by sanding and respraying. Because it is non-reversible after about 5 days (Wikipedia), it will not simply re-melt as plain lacquer does; sand and respray, and test any stripper on scrap first.

Safety and environment

Highly flammable (flash point -0.4 F on Mohawk's sheet); ventilate and use a NIOSH-approved respirator. The DuraCoat SDS lists formaldehyde at under 0.1%. No food-contact claim is made here. The EPA's federal limit for architectural lacquers is 680 g/L (40 CFR 59), a separate regime from these industrial products; Mohawk's sheets give the product figures.

Related

• Nitrocellulose lacquer: the plain version
• CAB-acrylic lacquer: non-yellowing lacquer without a pot life
• Conversion varnish: step up in chemical resistance
• Spraying with HVLP, Rubbing out a finish