Painting Preparation Q&A
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I'm currently painting the inside of my house. The walls currently are painted with a semi-gloss finish, which has been on them for around 20 years. I have used TSP to clean the walls. Is there a way I can paint over the old finish without having to sand the walls?
K in Scranton, PA
Sanding can be avoided in two ways. First, you can use a heavy duty primer sealer as a first coat before applying your finish paint. The oil based products, such as Kilz and Zinsser Cover Stain, will stick to anything (even glass), and give a good stable surface for top coating.
If you prefer not to use a primer, you can use a deglossing liquid such as Wilbond. The deglosser cleans and prepares the surface for repainting. If the original paint was latex, deglossers make its surface slightly tacky. If the original paint was oil, the deglossers are less effective... a light sanding to scuff up the surface might be desirable before using the deglosser, or instead of it.
If you want the best of both worlds, use the deglosser immediately prior to priming... the deglosser will remove any remaining oils or grease that the TSP missed, and prep the walls for the best possible adhesion of the primer.
You mentioned in one of your articles that TSP was not just a cleaner but also a deglosser. Would you recommend using it to degloss paint prior to repainting? Isn't TSP dangerous to use? Finally, you also mention a product called Wilbond for deglossing. Could you explain a little further?
KD from San Diego, CA
TSP is a powerful cleaner that can remove the gloss from not only paints but other sensitive surfaces. However, its primary function is cleaning, not deglossing. The deglossing effect is why TSP should never be used as a cleaner on a painted surface UNLESS you plan on repainting... it will make the paint more porous and consequently it will become dirty and actually grow mildew more quickly! There are some siding cleaners available now that actually inhibit the growth of mildew for a time after cleaning. Check at your hardware or home store for available brands.
As for Wilbond, it is a mixture of various solvents...including toluene, methanol, acetone, naptha and isopropyl alcohol.. that essentially "attacks" the surface of paint, softening and slightly roughening it so that new paint coats will stick better. It also removes oils and grease from surfaces making them more paintable. Wilbond works best on latex paints, but is an excellent cleaner for oil paints and metal surfaces (though if the metal has a lacquer or other preservative coating the Wilbond may damage or remove it!).
Wilbond is very easy to use… just wet a lint-free cloth with it and rub the cloth on the painted surface until the surface gloss diminishes. Latex paint surfaces will become tacky… oil paint surfaces will not. The effect is good for up to a half hour, depending on the temperature. Careful… avoid getting Wilbond on any other surfaces or you risk damage, especially plastics.
Both of these products are potentially dangerous, but for different reasons. TSP is banned in some places because of its phosphate content. Years ago it was determined that phosphates in detergents can cause havoc with the ecosystems of rivers and lakes. The phosphates promote the growth of algae, which in turn grow wildly and can actually kill off other life by removing the oxygen in the water.
Wilbond is a strong solvent and, when used without adequate ventilation, can potentially cause various brain and nervous system problems. This, of course, is true of many solvents and they all should be treated with respect and the manufacturer's warnings ALWAYS heeded.
Both of these products are potentially dangerous, but for different reasons. TSP is banned in some places because of its phosphate content. Years ago, it was determined that phosphates in detergents can wreak havoc with the ecosystems of rivers and lakes. Phosphates promote the growth of algae, which in turn grow wildly and can actually kill off other life by removing the oxygen in the water. Be environmentally conscious and legally prepared by consulting a lawyer if you are unsure TSP can be used in your location.
Wilbond is a strong solvent and, when used without adequate ventilation, can potentially cause various brain and nervous system problems. These effects can be temporary or permanent causing cloudiness of thought to severe injury. Amazingly (and a little "scarily") inhalation of these solvents can effect a person's driving enough that they may be pulled over for a DUI or cause an accident!
The moral lesson is... be safe and keep your work area ventilated! And remember, this effect is true for many solvents, not just liquid sandpaper. They all should be treated with respect and the manufacturer's warnings ALWAYS heeded.
I have an old file cabinet which I spray painted black and yellow 30 years ago. Wanting it to blend in better with my beige walls, I bought some beige spray paint. I did not bother to sand the file cabinet before repainting it. It took many coats to cover the black, but most of it turned out just fine...except for blisters on three of the four drawer fronts. Why did this happen? Is this due to spraying too thick a coat in one place? Why in only 3 spots, and not all over the big cabinet? Is it because the drawer fronts were lying face up when sprayed? But one drawer front, and the top of the cabinet, turned out fine.
Finally, what do I need to do to repair the blisters?
Tsk, tsk, tsk... no prep, eh? You are fortunate that anything stuck at all, though in time you may get more peeling. The drawer fronts may have been more in need of sanding and cleaning than the rest of the cabinet surfaces because of the fact that drawers get lots of close human contact! They are always being touched, so they tend to buildup accumulations of oils, grease, polishes, waxes, and cleaners… baddies that paints just don't like to adhere to.
Of course, there is the possibility that you may have sprayed too heavily or waited too long between coats. Spray paints have a window of time during which you can apply additional coats… usually within five to ten minutes of the first coat. If you wait longer than that to apply additional coats, you must wait at least a day before applying the next coat. Otherwise, the new coating of paint can cause the first coat to soften and release from the surface. This might not occur instantly… but will eventually appear as easy chipping or blistering. The label on the spray can will give you your marching orders.
To repair a few isolated blisters, let the new paint dry at least a few days so you have a hard paint film. Sand off as much of the new paint as necessary until you get a smooth surface. 220 grit sandpaper should do the job nicely. Then respray the entire drawer front. However, if the blisters are widespread, sand all the old paint off. Then, wipe the drawer front down with Wilbond, a cleaner and deglosser that prepares surfaces for painting. It is also known as "liquid sandpaper". This will remove the oils, etc that caused the original problem. Then you should be able to successfully repaint them. A word of caution… don't ever use Wilbond on a freshly painted surface. It is reactive enough that it could cause the paint to dissolve or even slough off!
Another option would be to use a primer before repainting the drawer fronts, but be careful in your selection of the primer. If it is not compatible with the spray paint, you will have another mess on your hands!