About Fiberglass Part 1 - Background + gelcoat care and protection February 18, 2018 23:06

The story of Fiberglass

Fiberglass itself is very fine fibers of glass (Duh!).  Although almost certainly seen before by glassblowers, in 1932, a worker at the Owens company in Illinois tried to weld together glass blocks and when a jet of air hit the molten glass fibers  (looking like Candy floss) were formed. Later, in the commercial preparation of glass fibers, steam is used instead of air.

 In the 1930s Owens Illinois expanded and later combined with Corning to form Owens-Corning.  In 1936 fiberglas® (only one s) was trademarked and patented.  It was used (and still is) for insulation, but then the company began research on spinning the fibers into cloth and introduced a heat treatment to give the cloth more flexibility. In 1942 Owens-Corning partnered with the USAAF to develop plastic laminates.  The fiberglass cloth was impregnated with resins and in 1944 the first fiberglass-reinforced plastic boat hull was made, eventually followed by fishing rods, kitchens trays and finally pleasure boats. From 1953 fiberglass laminates were used to make most boats, RVs, some specialized cars, shower stalls, bathtubs, hot-tubs even swimming pools and park slides.

How are glass-reinforced fiberglass items made?

Fiberglass items are made in a female mold with a smooth inner surface covered with a silicone-based release agent. This stops the resins from sticking to the mold. In making a boat hull, layers of fiberglass mat and woven glass fiber are impregnated with catalyzed resin and laid up one at layer at a time.  Polyester resin is most commonly used but sometimes other resins may be used. These include  epoxy resin that is more expensive but tougher with better bonding properties and is much more water-resistant. Also used is polyvinyl ester resin that has properties between those of polyester and epoxy it is also water resistant for use under the water-line.  Kevlar or carbon fiber may be used for reinforcement. of the laminate, Kevlar (used in bulletproof vests) may be used to reinforce the bow of boats for more protection against collision damage.

Use of carbon fiber results in a great increase in strength to weight ratio. Carbon fiber is commonly used in making items that  have to be light but very strong, such as spars. Vacuum bagging is used in making spars to ensure that there are no air bubbles and to make a much denser laminate.

Often, glass fiber laminate is sandwiched each side of other materials. Plywood is used as the central core for extra strength. Sandwiches of balsa or plastic foam can be used for strength with lightness.

The outer finish is usually composed of resin containing color pigment. This is called gelcoat. It is sprayed into the mold before applying the layers of resin impregnated fiberglass. The gelcoat stripes on the boat are applied first and are usually very thin. The smooth inner surface of the mold is covered with a wax-silicone mold release agent, so that when the hull of the boat is removed from the mold it is already smooth and shiny, just like a new car but without the labor costs of preparation and spray painting. This also means that the outer surface of the gelcoat already has a protective layer of weathering protection.  

How does the outer gelcoat surface break down?

Aging of the gelcoat is primarily caused by oxidation, just like rust on an iron or steel surface.   As gelcoat oxidizes, the long-chain polyester polymer chains break into smaller and smaller pieces,  eventually yieldng chalky material.  There will also be some partially oxidized material that is softer than the original gelcoat and often of lighter color.  Also the pigment in the surface layer may fade in the sun. Although surface oxidation is fairly easy to remove with abrasives, some partially broken down and some good gelcoat will also be removed. 

In a way also analogous to rusting metal, this oxidation starts to eat down into the underlying gelcoat, to form “pores” or “micro-crevices” that increase porosity of the gelcoat. Since these pores are full of chalk the chalk absorbs stains such as diesel smoke and rust. Sometimes strong acid cleaners are used to remove these stains (by dissolving the chalk) but this makes the gelcoat even more porous.

Left without attention, gelcoat can eventually become so porous that it cannot take a shine, after the conventional methods of compounding, polishing and waxing.  Furthermore, on black or dark-colored gelcoat, the chalk in the pores also makes it impossible to restore full depth of the color even with wet sanding and much abrasive compounding that will make the gelcoat layer dangerously thin.  There will always be a grey “shadow” that can only be removed chemically (as described below).

Care of  gelcoat and protection against weathering.

Superficial oxidation is easily removed by conventional methods of compounding,  polishing  and then sealing the surface with wax.

This process also removes some of the good gelcoat but can only be done so many times , especially on the thin gelcoat gelcoat stripes, where  the edges are very susceptible to “burn through” by the buffing  process.

By contrast, ISLAND GIRL®'s Cleanser-Conditioners and ELIXIR™  selectively dissolve out the oxidation without affecting the gelcoat itself. This is because the small molecules of chalk and partial breakdown products are more soluble than the long chain polyester polymers of completely sound  gelcoat. This is not the same as with some non-selective solvents like acetone that will dissolve and removal oxidation AND of good gel coat.

Another drawback to the use of (even very fine) abrasive polishes is that, by producing microscopic scratches, the oxidation process is speeded by greatly increasing the surface area of raw gelcoat susceptible to oxidation. This happens because wax may seal against water but NOT the air needed for oxidation. That is why the ISLAND GIRL® System is perfect for use on  NEW boats.

Water-based acrylic coatings

An alternative to the use of wax is to clean the gelcoat and then seal it with a clear acrylic coating. Best results would be expected with solvent-based acrylic but thorough dewaxing and wet sanding would be required for good adhesion, and when the coating eventually goes grey and opaque, is would need to be sanded off.

Of course, there are also several water-based acrylic coatings, of which the main one remaining is Poliglow™ . They can give satisfactory and very durable results because they do seal off the pores and would therefore protect better than wax. However, it is essential to first remove all traces of wax before application, otherwise the finish will flake off. Similarly thay cannot sufficiently adhere to  new or painted surfaces (unless first wet-sanded). They really can only be used on older gelcoat that is porous, so that the pores actually provide the “key” for adhesion of the coating.   Such coatings eventuall become grey and have to be removed by an ammonia–based chemical stripper.  More important, by becoming grey in the pores of the gelcoat, they can only be properly removed by deep wet-sanding.

Another drawback to the use of water-based acrylic coatings is that they require about six coats (sometimes as many as 12) using a special applicatory to minimize “lap marks".  Being water-based these coatings can only be properly applied in warm dry conditions on a boat that is pulled out the water.


Unique Properties of the ISLAND GIRL® System for care and restoration of gelcoat

This product system can be applied to a boat in the water under less than ideal conditions from the dock or from a dinghy and can minimize the problem of stress cracks by sealing the cracks.

 ISLAND GIRL® Cleansers and ELIXIR™ are designed to dissolve out all the chalk in the pores as well as on the surface and soften partially broken-down gelcoat so that it is easily removed by mild abrasion by a scuff pad.  Oxidation in the pores is drawn up to the surface into paper towel soaked in the product.  

Then, in the case of our Cleansers and ELIXIR™, the product dries back leaving the pores soaked in anti-oxidant conditioner while restoring  depth of color by removing the greyish chalk.  ELIXIR™ also leaves a wax-resin coating on the surface. The fluorescing agents in our Cleanser-Conditioners and ELIXIR™ also “brighten” white and colored gelcoat. Therefore the UV is sunlight is “pacified” so that it no longer causes damage but actually improves the the durability and appearance  of the gelcoat surface. An outer coating of MIRROR HARD Superglaze™ can be used for extra weathering protection and astounding “better than new” shine.