Conversion varnish

Overview

The EPA's architectural-coatings rule (40 CFR 59.402) defines conversion varnish as "a clear acid curing coating with an alkyd or other resin blended with amino resins and supplied as a single component or two-component product", in which film formation is the result of an acid-catalyzed condensation reaction. Wikipedia's comparison table says it meets the "severe use" standard, is difficult to reverse and makes an excellent hard finish. It is the usual choice for cabinet shops, and Mohawk and Finishworks sell it for kitchen cabinets and furniture.

Not to be confused with General Finishes' water-based "Enduro Conversion Varnish", which is a two-component urethane; see Catalyzed polyurethane (2K).

Pros

• Tough and hard: described by Wikipedia as an excellent hard finish, and Finishworks says AristoMax meets or exceeds KCMA, the kitchen-cabinet test (maker claim).
• Fast: AristoMax is touch dry in 20 minutes and recoats in 45 to 60 minutes; AristoVar is dust-free in 15 minutes and recoats in 60 (Mohawk).
• AristoMax is low VOC at 250.24 g/L (maker data).
• AristoMax can be rubbed out after 24 hours (Mohawk) (Rubbing out a finish).
• Finishworks describes AristoVar as lower in solids, economical, "closer to the wood" and "silky" (maker claims).

Cons

• Needs a catalyst and has a pot life: 8 to 12 hours for AristoMax and 24 hours for AristoVar.
• Recoat window: for AristoMax, if the second coat cannot go on within 4 hours, wait 24 hours and scuff-sand with 320; sand immediately before recoating AristoVar.
• Difficult to reverse (Wikipedia), so repairs are hard.
• Higher VOC than other options: AristoVar is 566.61 g/L, above the 450 g/L federal varnish limit but under the 725 g/L conversion varnish category in 40 CFR 59; local rules vary.
• Spray equipment and a booth are needed.

Suitability

A professional-shop finish for kitchen cabinets, vanities and furniture on hardwoods such as Red oak, White oak, Hard maple and Hickory. Fill open pores first if wanted (Grain filler (pore filler)). For finishing sheet goods see Finishing sheet goods (plywood, MDF, MDO).

Coats and application

Prepare the surface (Sanding schedule) and spray (Spraying with HVLP). Mohawk AristoMax: 4 oz of catalyst M59C0080 per gallon, pot life 8 to 12 hours, touch dry 20 minutes, sand and recoat at 45 to 60 minutes, rubout at 24 hours. AristoVar: 8 oz per gallon of catalyst M59C0037, pot life 24 hours, dust-free at 15 minutes, sand and recoat at 60 minutes. Use the catalyst number printed on the specific product's sheet.

Compatibility

• Use the catalyst the data sheet names for the exact product.
• Follow the sheet's sanding-sealer advice; see Sanding sealer (and vinyl sealer) and Dewaxed shellac.
• Not to be interchanged with water-based 2K urethanes (Catalyzed polyurethane (2K)) without a test.
• The AristoMax SDS lists incompatibility with acids, bases and oxidizers.

Care and repair

Clean with a damp cloth. Because the film is difficult to reverse (Wikipedia), damage is repaired by sanding and respraying within the sheet's guidance. Rub out at 24 hours (AristoMax).

Safety and environment

Flammable (flash point -4 F for AristoMax, 39.2 F for AristoVar). Spray with ventilation and a respirator. The AristoMax SDS lists formaldehyde under 0.1%; AristoVar's sheet gives a HAPs-related VHAP ratio of 0.35. Low-VOC and formaldehyde claims are manufacturer data. The federal limit for conversion varnish is 725 g/L (40 CFR 59). No food-contact claim is made here; see Food-safe finishes.

Related

• Catalyzed polyurethane (2K): two-part urethane alternative
• Pre-catalyzed and post-catalyzed lacquer: easier catalyzed lacquer
• Alkyd varnish: non-catalyzed alkyd
• Spraying with HVLP, Rubbing out a finish