How to clean old paint layers with paint stripper

There are many reasons why we want to remove the old finish coat from doors, furniture or other objects: the paint coat is cracked or skipped, the current colour is too dark and we want a lighter one, the wood is painted and we want it varnished to show the grain, we don't know what the original paint was and we don't want to risk the new coat peeling, etc. One of the preferred methods of removing old coats is stripping. Why it is a preferred method, how stripping is done, what materials are used and how the wood is prepared for repainting is explained below.

When stripping is the recommended method to remove paint from the wood surface

According to the DEX, pickling is the removal of grease or oxides from metals. The term has, however, also been adopted for cleaning wood, and the solution used for this purpose is called paint stripper. Pickling solution names in Englishpaint removeror in Italianpaint stripper,are more accurate because they refer strictly to paint removal. But the market has adopted the term paint stripper and under this name you will find solutions in specialist shops.

We choose pickling especially when the shape of the object or the carvings present on the surface of the wood make it removal of old paint layers by other methods to be very difficult. The most suitable method for such surfaces would be sandblasting with softer abrasive materials (baking soda, shredded walnut shells, corn cob husks), but it is harder to find wood sanding specialists and, besides, the method is expensive.

Stripping does not require high costs or special equipment or skills. Patience is needed because it is not enough to apply a coat of paint stripper and the problem is solved. Most of the time the procedure needs to be repeated 2-3 times to remove the paint completely. After the paint stripper has been applied, the paint will soften and must be removed with a scraper. On difficult surfaces thin tools should be used and often the surface also needs to be washed with thinner to clean the wood thoroughly. I did this when I cleaned the doors of the Pitar Moș church. Find heredetailed step-by-step information.

Are there more than one kind of paint stripper or just different brands?

Paint strippers are solutions that attack the paint, making it much easier to remove. They are either very aggressive solvents or acids or bases that attack the bonds inside the resin, destroying it. Restrictions on the use of some products now considered hazardous to health have made paint strippers less and less aggressive. In a way, I agree with those who say that "in their day", paint strippers were better. Yes, they were much more aggressive and very rarely needed to be repeated, but they were also much more dangerous.

The three main types of paint strippers

• Aggressive solvent mixtures
• Pickling solutions for natural oils or alkyd paints and varnishes
• Universal waterborne pickling solutions

Solvents are used more in factories because their strong smell is hard to bear. In factories there are high-performance exhaust systems that remove solvent vapours, but even so it is hard to work without a mask and protective equipment.

Paint strippers for alkyd oils and paints are caustic soda-based. They attack the inner bonds in the resin turning the paint, oil or varnish into a liquid that is washed away with water. The problem in this case may be the water used for washing. On old and sensitive items, too much water may not do any good. But if the wood is sound, the method is preferable because it removes old coatings simply and well.

Universal water-based paint strippers are the most used. They are generally in gel form because they take time to work. If you have a choice between a liquid stripper and a gel stripper, choose the gel, it's much more effective. The differences between the different brands are due to the concentration of the active substance, hence the greater or lesser effectiveness of the respective products. Only by testing them can you determine which is better. Until recently I thought that Decanol from Policolor was a good paint stripper. I even recommended it many times. I worked with it 8-10 years ago and it was very effective. Two months ago, when I worked on the doors of the Pitar Moș church, I tested three paint strippers: Decanol, Dekapant gel Kober and Supralux Extra Strong Universal Paint Stripper. Of all of them, Decanol was the weakest, Supralux paint stripper was far more effective.

Paint stripper application and removal

The paint stripper is applied with a brush, in a not very thin layer and left for the time recommended by the manufacturer, usually between 20 and 30 minutes. During this time the paint layer softens and sometimes wrinkles a little. Paint stripper does not work well at very low temperatures. At high temperatures drying should be avoided. A well wrung wet cotton cloth placed over the top prevents drying and can increase the effect on the paint layer.

The soaked layer is removed with a scraper, narrow chisel or wire brush with thick brushes and bonnets. Brushing is effective when the surface has intricately patterned carvings. It is not simple and takes a lot of patience. Soaked varnish often clings to the brush and must be left in thinner to clean thoroughly. If the surfaces are straight, cleaning is easier and quicker. Very rarely does the surface clean completely in one operation, but the hardest is the first time. Over time the paint becomes softer and easier to remove.

After complete removal of the paint layer, the surface sometimes remains tacky and should be wiped off with a thinner recommended by the paint stripper manufacturer. If there is no such recommendation, use a wash thinner or universal thinner. If wiping with a cloth is not sufficient, apply the thinner with a brush and then wipe with a clean cloth.

Preparing wood for repainting

Before repainting it is recommended to sand the wood as in the case of white grinding. The old finish has entered the pores of the wood and to ensure even staining and adhesion of the coats to follow, the pores must be opened. This is the purpose of sanding. If staining is attempted without sanding, the wood may not absorb enough and light stains may appear.

Sand with 150-grit sandpaper, even 180 or 220 if the wood is sanded or sanded (plop). Then dust with a cloth. Dust from sanding spoils the appearance and reduces the adhesion of varnish or paint layers.

I hope you find the information interesting and useful. We always welcome additions. And if you have any questions or queries, please leave them in the space below. I'm sure I'll answer them.