Polyurethane caulking bonds very well and has a rubbery, paintable texture once applied. It can be very difficult to remove once it’s on, though, and it seems that only good old elbow grease will do the trick. However, a few methods and products can increase chances of success in removing polyurethane caulking.
Step 1 - Dampen
Use water to soften old caulk.
Step 2 - Chemical Remover
You will probably need to try several methods. Chemical removers, such as paint strippers or caulk removers, are used to soften caulk so that it is easier to scrape off. Be sure to put down newspaper or protective covering under the area where you are working. Also, make sure you are working in a ventilated area.
To use the chemical remover, apply a thick coat to the caulk you wish to eliminate. To keep it from drying out, put wax paper over it. Read the product instructions to determine the length of time you need to let it sit.
You’ll be able to start removing the remover and the caulk once you notice the surface is bubbling. Use a second coat if necessary.
Step 3 - Scrape
You can remove polyurethane caulk using a painter’s 5-in-1 tool. This special tool is a spreader, scraper, putty knife, crack-patcher and paint remover all in one. It has a flat edge, a series of comb-like teeth, and a semi-circle (meant for running along a roller to remove extra paint.) It’s not expensive (generally under $10) and small enough to go in your pocket. It can be made of wood, plastic or metal.
You might find a box cutter or razor to be useful in removing caulk as well. Anything that can get underneath the old caulk and dig it out might come in handy.
Step 4 - Chisel
Since polyurethane forms a very strong bond and can be extremely difficult to remove, go to the hardware store and have a look around. What you come out with might not only surprise you, but it might work as well, especially on a concrete area like a pool. A ¼-inch chisel and a utility knife can do the trick. Use the utility knife to make a vertical cut into the stubborn caulking. This will give you a spot to get the chisel under the caulking to peel it off. Stop often to sharpen the chisel.
Step 5 - Steel Wool or Wire Brush
Once you have the majority of the caulk removed, you might still need to clean up the area. To get in the crevices, use steel wool and a wire brush to scrape residual pieces of caulk.