Bathtub Reglazing

Curing A Bathtub With A UV Lamp

In 2009, Orlando Florida based Midwest Chemicals announced the availability of a “totally green” no VOC bathtub refinishing solution, a UV cured tinted base coat and clear coat process that is said to cure in 2 seconds, and can be spot repaired immediately if needed. This process has the claim to forever change the bathtub refinishing industry.

A very heated debate about whether or not UV curable coatings work for bathtub refinishing has sparked an interest to us here at the BATHTUB REFINISHING ASSOCIATION OF AMERICA. The aspect of going green using a low VOC coating that cures instantly in the bathtub refinishing industry is one that raises the eyebrows of specialists nationwide. The question is; does it work?

In a recent discussion with a well known chemist and coatings developer who has been developing UV curable coatings for 15 years explained the technicalities and addressed a few issues with the process.

This is what was said:

“The proper curing of UV coatings requires a specific amount of UV exposure, typically in the 250 to 365 nanometer spectral range usually at 300 watts per inch for a defined amount of time to meet the dosage requirements. Once the UV light excites the free radicals in the photo initiator, the coating polymerizes instantly.

When dyes or pigments are used in a UV coating, if applied to thick, (spraying on a little too much to cover a shady or dark area), they can obscure or block the UV from reacting with the photo initiator leaving lower layers of the coating uncured. If this occurs the coating properties are greatly diminished in two primary ways, loss of adhesion and moisture, chemical resistance. Additionally, yellowing can occur over time and in this state blocking cannot be overcome with additional exposure time which will eventually damage the finish if overdone. So no matter how much energy you throw at it the light simply can’t get through.

The problem with this scenario is that it is very difficult to determine cure through without damaging the finish by performing a cross hatch adhesion test. Visually and to the touch the coating will appear to be cured, it will be hard and scratch resistant but in reality it is not fully cured in the lower regions which will eventually cause failure.

The uncured material, is exactly that and if some of the coating were to flake off, say when a mother is bathing her baby, skin burns could occur from the acrylic acid, which is commonly used and a necessary component in UV coatings.

One can make claims that UV is easily spot repaired, simply sand a little and put a little more on, cure it and you are done. In the above scenario a simple repair would not be realistic, because when the coating is applied it is usually applied in a uniform thickness which means the majority of the surface would have lower regions that were under cured. The only solution to this problem would be to chemically strip the failed coating off. Strippers usually contain methylene chloride which we all know is nasty stuff but it usually gets the job done. Not so with most quality UV coatings, they are typically very resistant to methylene chloride and every other solvent you can name. This means the only choice you have is to sand it off and it is hard to sand.”

With these issues in mind, it seems that this process still needs to be refined and perfected in terms of usability and before final application on someone’s bathtub. I would only hope that upon release to the public these issues would be worked out. I do agree that the potentials for this breakthrough are quite remarkable and if time proved to be a success will forever change the bathtub refinishing industry.

In conclusion:

The bathtub refinishing industry is an industry that is suffering at the hands of inexperienced refinishers and failed processes. If this failure rate continues, the bathtub refinishing industry will soon become a pariah in the remodeling community. We as refinishers owe it to the public to be the very best we can by understanding what works and what does not. Before running out and trying something new on someone’s bathtub test it first on an old junkyard bathtub. Cross hatch tests are easy to perform and by doing this you ensure your success and the success of the bathtub refinishing industry. This should be done with all materials you use whether it is UV or solvent. If you have any questions about UV coatings as it applies to bathtub refinishing,  click here to log into our forum, or, you can contact the BATHTUB REFINISHING ASSOCIATION OF AMERICA.