This is THE number one most important process that anyone should master before applying paint to anything.
I recently refinished a section of the 100 year old cement, car oil-soaked surface that my mechanic's shop was in. He had purchased some 'magic' paint product off the internet and simply used Pinesol to clean the cement before spreading this semi-water-based, two part epoxy type paint on the surface. I'm amazed it even stuck as much as it did! What happened though was typical: the oil bled up through the paint and created dull, ugly spotting all over that was uneven - and unnerving to say the least. What he didn't understand was that he should have taken the time to use BOTH TSP and muriatic acid to strip the cement bare before applying any type of paint. All I could do was TSP it all and reapply a more industrial paint to go over the bad prep job underneath, and it already is better.
For furniture, the process is a little different. But nonetheless, still important so that the end result will give you a paint finish that not only will retain the type of sheen you want, but be as durable and lovely as possible.
STEP #1: De-Gloss the shiny surface
STEP #2: Sand the surface with a sponge-like hand sander. *this type of sander will allow for easy access to curves in the furniture's surface.
STEP #3: Use Simple Green for interior cleaning & thorough rinsing (hot H2o)...
...TSP powder - avoid the 'green' version as it really is pathetic - (hot H2o, heavy duty dish gloves, and fresh sponges to rinse)...for kitchen & bath cabinets and exterior furniture.
1) Is the surface of your piece shiny? Does it have a glossy finish or varnish? Is it plastic or laminate? Fresh paint needs something to grab onto. Slick, glossy surfaces don’t give it much to bite into. If your piece is slick and/or glossy, wash it first, then take some 220 grit sand paper and de-gloss it. This does not mean sanding ALL the finish off. It means to scuff it up a bit so it is not so shiny. This will give the paint something to stick to, and only takes a minute or two.
2) Is the surface of your piece rusty or covered with chipping or flaking paint? This will require a little bit of sanding. Most high quality paint sticks to whatever you paint it on – and if that is flaking, peeling or chipping, so will the paint. Just take some 80 or 60 grit sandpaper and sand down the flaking/peeling/rusty parts, then clean off your piece. If it was REALLY rusty, you might want to spray some Rust Inhibitor and RUSTOLEUM makes a good product for this. After the surface is smooth and completely primed, you're ready to apply the new paint.
STEP #3: Remove all rust and Prime
3) Has your piece been sitting outside for a while? Chances are it is covered with some sort of outdoor dirt, pollen, bird poo or tree sap. Although paint can provide a strong surface, it won’t remove bird or insect poop! Clean your outdoor piece with TSP and HOT water, use a wire brush (metal surfaces) or very stiff nylon toothed scrub brush to get into the grooves and curves of bamboo, wooden or vinyl-strapped pieces, then rinse it off. Let it dry completely in the sun and finish off with a nice 100% cotton rag, then spray prime it.
Now you are ready to apply the exterior paint product of your choice.
If you are painting your kitchen or bath or other hard furniture cabinets: These types of cabinets get handled frequently. Cooking grease, body oils from fingers, food splatters, soap and 'wet dust' build up on them. Before you paint them, clean them really well with TSP and HOT H2o, then rinse extremely well with fresh sponges - and more than once before drying off with 100% cotton rags.
After all, don't you want them to come out looking like this....