Defects in Fiberglass Pool Gel Coat: What Causes Them?

There are typically two types of ‘blems’ we see:

• Damage that occurred after manufacturing
• Defects that occurred as a result of manufacturing

The damage that occurs post-manufacturing is pretty self-explanatory:

• A rock struck the pool during shipping
• The installer drops something (rather large) in the pool, etc.

This is simply a case where something damaged the pool after it left the manufacturing plant. In this case a gel coat repair is performed, and with any luck it’ll match up pretty well and you're on your merry way.

But that’s not what we’re talking about today. We’re going to discuss gel coat defects that occur as a result of manufacturing, and that boils down to one thing: proper mold maintenance. 

Fiberglass Pool Mold Preparation and Maintenance 

Here are some fiberglass pool mold FAQs:

What is the Mold?

The mold is basically a fiberglass pool in reverse. Think of it like this: If someone were to make an exact replica of your face, they would apply plaster to the front of your head, wait for it to harden, then pop it off, revealing a 3D mirror image of your face.  The same principle applies to a fiberglass pool, so in this case your face is the mold and the pool shell is the mask that’s produced from it.

Why is Mold Preparation So Important?

Imagine if the entire world were to view your mask and the day they applied the plaster, you had a huge zit on your forehead! The zit would also show up on the mask, right?....and worst of all it would be on every mask made from your face until the zit went away. 

The same applies to fiberglass pools. Any dirt, dull spot, or blemish that’s on the mold will also appear on the pool. In other words, the pool is a mirror image of the mold. 

How are Fiberglass Pool Molds Prepared?

Each and every time a fiberglass pool is built, the mold must be stripped, buffed, and waxed to ensure the mold is pristine and the new pool can be “popped” away from the mold without causing damage. Any blemishes on the mold must be repaired even before this process begins.

What Are the Consequences of Poor Mold Maintenance and Preparation?

Pools that are “shot” on molds that have not been properly maintained have blemishes, dull spots, or ‘mold marks’.  A distinguishing feature is that the gelcoat (surface layer) of the pool may appear to have a crack, pit, or other defect, but upon further inspection you see that the ‘blem’ actually stands out from the pool shell instead of being recessed into it.  This results from the gelcoat filling the void that existed on the mold. 

Most times these issues can be easily remedied and sometimes that’s just not the case. But every fiberglass pool manufacturer knows that investing the time and energy required to properly maintain and prep their molds is far better than the windfall that occurs when the molds are neglected.

By and large most, if not all, fiberglass pool manufacturers do an adequate job maintaining their molds, so this is no means an epidemic in the industry. But anything that affects the quality of a fiberglass pool is worthy of discussion, in our book anyway.

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At River Pools, we manufacture world-class fiberglass pools for customers across North America. If you'd like to get a fiberglass pool for your home, you can check out our catalog of models, try out our pool pricing calculator, or request custom pricing using the button below. 

You can also download our free ebook to learn more about how to buy a fiberglass swimming pool. 

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