Urethane Caulk Benefits
Solvent based caulks came under scrutiny by the EPA because they contain mineral spirits/solvents that contribute to air pollution as they dry and/or cure. The solvents that allow them to flow from the caulk tube evaporate into the air and create smog.
For years, the water based caulks have made steady improvements. The first generation ones were somewhat hard and had poor adhesion qualities. The water based caulks of today are awesome. They have better flexibility, better adhesion properties, and they adhere much better to smooth surfaces.
A water based caulk that has been around for nearly 40 years hidden back in the shadows is urethane caulk. Urethane caulks are exciting because they are similar in many respects to the popular silicone caulks. But, in my opinion, urethanes are better.
Urethane caulks will give you these benefits:
- High Tear Resistance
- Low Shrinkage
- Water Resistant
Urethane caulks adhere very well to vinyl siding, cedar wood, aluminum siding or gutters, and brick. The only thing they don't stick well to are the polycarbonate plastics. This plastic is the type used for those old fashioned bubble type skylights. Surely you don't have one of those, do you?
One of the reasons urethane caulks stick so well is that they actually bond to things by crosslinking on a molecular level. If you get some on your skin and don't wash it off quickly, it will be there for a few days until the oils from your skin finally loosen it.
Patience is Required
You will note that I said that urethane caulks are paintable. It is true, but you must allow them to cure before you paint them. The curing process can take up to 7 days. This is why you don't see many professional painters use them. They want to caulk and then be able to paint in a few hours. This is a shame since the urethane caulks perform much better than the acrylic caulks.
Ultraviolet (UV) Light Problems
Sunlight can degrade urethane caulks that are not painted. The caulks begin to chalk like old fashioned paints. They still bond well - they just don't end up looking so good. The urethane caulk that offers the best UV resistance is one that is made for marine use. OSI Sealants makes a marine urethane caulk.
You can stop UV degradation by just painting the caulk after it is cured. This is where patience pays off.
Have you seen the caulks with the 20, 25, 30 and 50 year warranties? How can they make these claims? Well, most of it is marketing. I guess some of the manufacturers feel you will not keep the tubes, receipts, or even have a clue as to what you used when and if the caulk fails. I can tell you that the longer the warranty on the tube, they better the caulk is inside.
How much caulk have you wasted trying to stick a nail in the end of the tip? I have sure wasted my share.
A top caulk chemist shared a secret with me that I have yet to verify. He said that if you wrap the end of an open caulk tube with Saran Wrap brand sheet plastic - a double layer mind you - and then tape it tightly, the caulk should not dry out for a long period of time.
Caulks can and do dry out in the tube. They have shelf lives of perhaps 12 to 18 months. Some manufacturers are beginning to put expiration dates on the tubes. Look for these when you buy caulk.