You would not want the same coating that is designed for refinishing a Cast Iron Bathtub to be used on a Fiberglass Bathtub. If you own a fiberglass bathtub you understand how the surface will flex when you step in and out of the tub. Could you imagine having the ultra hard coating applied over a flexible surface such as Fiberglass or Acrylic? As the original surface flexes the new surface would begin to show cracks. Then water would penetrate those cracks and before long it would simply erode away your new surface. Much like a river eroding away the land the river is moving through. (See how I brought that visual comparison into play!) LOL.
The great news is, with professional refinishing their are ways to to allow for the flexible surfaces such as fiberglass and acrylic. The truth is a professional refinisher should know #1) Which product to use for the surface the application is for and #2) There absolutely is not a one coating works on everything method!
You will however, find plenty of refinishers that claim the coating they use works on any surface. I have a pretty good theory as to why they make that claim. Back when I first started refinishing in 1991 we were very limited on what we could use for refinishing. In 1991 there was not a synthetic porcelain coating. In fact we the simple truth was we had to experiment to see what worked, the refinishing industry relied on Epoxy paint and if it was going on a flexible surface, those of us that understood the properties of Epoxy knew we could back off a little on the hardening agent and get the coating to flex. The trade off was the coating would not be as durable but in those days Refinishing was mainly for Apartments, Hotels and Rental properties that simply needed a quick fix to get another lease term satisfied!
As the Industry became more main stream and coating manufacturing companies seen a market they started making technological advancements in the coatings used for Bathtub, shower, tile refinishing. First was the fact that refinishing technicians were begging for another option besides epoxy! Epoxy had a dull appearance, It made the surface look painted, It yellowed when bleach was used on it. (which is why the Epoxy D.I.Y. kits have a yellow tint to them, They say white but if you look at them they are slightly almond). The coating gloss, and durability began to advance and by 2005 After literally trying every new coating that came on the market, I started using this new product called Synthetic Porcelain. Synthetic porcelain was able to mimic the gloss of porcelain. Did not yellow when bleach was used, Had a smooth, tough as nails surface! By 2007 we had a full line of synthetic porcelain coatings which were specifically designed for the Bathtub, Shower, Tile refinishing industry. The development of synthetic porcelain for Fiberglass Bathtub Refinishing, Acrylic Bathtub Refinishing, Cultured Marble Bathtub Refinishing. We had the training and ability to etch the old surface which would expose pores and create microscopic scratches which would allow us to chemically weld a new synthetic porcelain surface into the old surface, not onto the old surface like paint!
I sincerely appreciate the time you took to read this information. I feel if I can educate the consumer about bathtub refinishing facts instead of just other peoples opinions about the bathtub refinishing process then you will share my passion and appreciation for the savings that can be realized through correctly refinishing a bathtub, shower or tile surface. <Bathtub Refinishing>