This topic has bothered me for many years and I have never managed to find a helpful answer. If I’m coating a previously painted surface, how do I know what type of paint was used. I assume it is important to know because water-based and oil-based paints are very different.
1. Is it possible to ‘prime’ an existing oil-based paint with universal undercoat and apply water-based paint over this? I prefer to use water-based paints because cleaning the brushes and rollers after use is so much easier.
2. Is there an advantage to using enamel over water-based paints?
A Toni Stella the Paint Fella replies:
Determining whether the surface was painted with a acrylic or oil-based paint is very important.
Testing for an oil base:
• Soak a cotton wool ball or very soft cloth in methylated spirits, alcohol or lacquer thinners and rub it back and forth over the area.
• If the paint rubs off (dissolves) and you see the other colour below, you know it’s a acrylic product.
• If no paint is removed, it’s an oil-based paint.
Oil-based enamels can sometimes be painted directly over acrylic (however, it is not acceptable industry practice). Special preparation is needed to cover oil-based paint with acrylic.
Covering oil-based enamels with acrylic:
• Surfaces previously painted with oil-based enamels must be abraded with a Scotch-Brite pad and a solution of sugar and soap.
• Rinse with clean running water and repeat until a matt surface is achieved.
• Apply a coat of Plascon Multi-Surface Primer and allow it to dry for four hours at 23˚C.
• Apply the final coat of acrylic paint.
• Your brushes and tools can be cleaned with water.
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