Question: We use an UV adhesive/sealant that we allow to cure in daylight. On some days, it cures slowly. Can we speed it up by using a full-spectrum bulb from the hardware store?

Answer: A full-spectrum bulb is only designed to simulate natural daylight. It will probably help a little, but you really need to discuss the composition of your adhesive with your supplier. These adhesives contain a photoinitiator, which decomposes under the light and generates free radicals to begin the curing.

There are two types of photoinitiators: those that decompose with ultraviolet (UV) light and those that use visible light. Light-curing adhesives are relatively recent inventions, and can also be cured using LED lamps. Your adhesive likely has a UV-type photoinitiator; these decompose with UV rays in the 350-380 nm region of the electromagnetic spectrum. A black light would probably give better results than the full-spectrum bulb, but you will need a fairly high-intensity UV lamp to get fast, reliable curing.

Question: We need an epoxy adhesive that cures in about a minute to fill some large cavities in a concrete and wood structure. The very fast cure is needed to prevent sagging of the adhesive—the application is in a vertical position.

Answer: You are unlikely to find an epoxy that will cure that fast. In addition, it would generate a tremendous amount of heat on curing. However, I feel confident that epoxy manufacturers can give you a fairly fast-curing product that will gel in 15-30 min. that will be non-sag. 

 Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.