Most trade sprayers settle on one system and stay with it, which is sensible. Changing systems means new mix ratios, new thinners and new habits. But the right system for a hall table is not always the right system for a kitchen that gets wiped down with a spray cleaner three times a day. This is how the three main solvent systems compare, and how we help customers choose between them.
The short answer
- Pre-catalysed (PC) is single-pack, fast and simple. Good for furniture, joinery and shopfitting where the finish is handled but not scrubbed.
- Acid-cured (AC) is two-pack with an acid catalyst. Harder and more chemical-resistant than PC. A long-standing choice for kitchens and furniture.
- Polyurethane (PU) is two-pack with a hardener. The toughest of the three, with the best resistance to wear, water and cleaning products. It needs isocyanate training.
The rest of this guide explains what sits behind those differences.
Pre-catalysed lacquer: single-pack and quick
Pre-cat lacquer has its catalyst built in. You open the tin, thin it for the gun and spray. There is nothing to measure and no mixed pot to watch.
On the Novalk pre-catalysed range, the clear topcoat thins at 20–30% ND4100 for a gravity gun and 10–20% for a pump. The sheet gives one hour before sanding the first coat and recommends two to three coats at 100 microns.
Where it fits:
- Bedroom and living-room furniture, shelving, wardrobes and display joinery.
- Shopfitting where the programme is tight and the finish is not exposed to heavy cleaning.
- Workshops that want one simple process for most jobs.
Where to be careful: PC lacquer is less resistant to heat, water and chemicals than the two-pack systems. On a kitchen worktop edge, a sink run or a bathroom vanity, a two-pack system is the safer specification.
Acid-cured lacquer: harder, with a long pot life
Acid-cured lacquer is mixed with an acid catalyst before spraying. On the Novalk AC range, the ratio is 10:1 with NCH999. The cured film is harder and more resistant to household chemicals than pre-cat.
A practical advantage of AC is pot life. The current Novalk AC clear topcoat sheet gives up to 72 hours with ND4100, which suits shops that spray across a couple of days. That does not mean leaving a pot uncovered all week. Label it with the time and ratio, as the catalyst and pot life guide explains.
Where it fits:
- Kitchen doors and carcasses, furniture and joinery that needs more resistance than PC.
- White and coloured Promatch work, where AC white base is tinted to the customer’s colour.
Where to be careful: acid-cured lacquers release formaldehyde while curing. Booth extraction and the PPE on the safety data sheet are not optional.
Polyurethane lacquer: the toughest film
Polyurethane is a two-pack system where a hardener cross-links the film. It gives the best resistance to wear, water, heat and cleaning products of the three, which is why it is specified for busy kitchens, commercial interiors and floors.
Each PU product has its own hardener and ratio. For example, the Sirca white PU Promatch topcoat mixes 1,000 ml of topcoat with 650 ml of CTH31 hardener, and the Lacquerite PU white primer mixes 1,000 ml with 500 ml of NC942. Stay inside one system: a Sirca hardener is not a substitute for a Lacquerite one because the tin looks similar.
Where it fits:
- Family kitchens, utility rooms and bathroom furniture.
- Commercial and hospitality interiors that are cleaned daily.
- Floors, using a dedicated product such as the Sirca PU parquet topcoat.
Where to be careful: most PU hardeners contain diisocyanates. Anyone spraying them needs the REACH training described in our diisocyanate training guide.
Where waterborne fits in
Waterborne lacquer is not a fourth solvent system, but it is now a real option for interior work. Modern waterborne topcoats, with a crosslinker added where the job needs more resistance, cover much of the furniture and joinery that PC and AC used to. If you are thinking about the switch, read moving a solvent line across to waterborne.
How we help customers choose
When a customer asks which system to use, we ask four questions:
- Where will it be used? A kitchen, a bedroom, a shop counter and a floor are four different specifications.
- How will it be cleaned? Spray cleaners and steam need a two-pack system.
- What does the workshop already spray? Changing system has a cost in training, stock and mistakes.
- Who is spraying? PU needs isocyanate training. If nobody in the shop has it, that decides the question for now.
Putting a system to work
Once you have chosen the system, the preparation underneath decides how well it performs. For painted MDF, see priming MDF for a painted finish. For kitchens being refinished in place, see the kitchen re-spray process. For steel and aluminium, the metal system is separate; see coating metal and plastic.
Do not build a mixed system
The most common failure we see is not a bad product. It is a primer from one system, a sealer from another and a topcoat from a third. Each product is designed to bond with the others in its own range. Pick a system and use its primer, sealer, topcoat, thinner and catalyst together.
If you are unsure, call the counter with the job and the sheen you need, or build a quote and we will confirm the full system before anything is mixed.