Category Archives: Techniques & Tips

Epoxy's adhesion to metal is affected by surface treatment

Effects of Surface Treatment

On Epoxy Adhesion to Metals

by Brian Knight—GBI Technical Advisor

Above: Surface treatment can make all the difference in epoxy adhesion to metal. Photo by Manny Becerra on Unsplash 

We have performed tens of thousands of adhesion tests over the years and many of these tests were done on metal surfaces. Below is a summary of tests done on a variety of metal surfaces and done with a variety of surface preparations. As you look at the chart, notice the surface preparation that gives the highest number.

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Epoxy vs. Polyester is an important consideration in fiberglass boat repair.

WEST SYSTEM Epoxy vs. Polyester

for Fiberglass Boat Repair

by Tom Pawlak — GBI Technical Advisor

Above: Epoxy vs. polyester in a typical fiberglass boat repair cross-section. 

Even though we’ve been promoting the use of WEST SYSTEM® Epoxy for repairing fiberglass boats (boats made with polyester resin) in our manuals and Epoxyworks for many years, we continue to receive inquiries asking whether it is appropriate to use epoxy for polyester boat repair. Because of the misinformation still prevalent in marinas, local yacht clubs and on the Internet, we felt it was time to restate the case for epoxy. Continue reading

Polyester Gelcoat Over Epoxy

by Jeff Wright — Vice President of Technical Services

Most production fiberglass boats are made with polyester resin, and we’re often asked if it’s appropriate to use polyester gelcoat over epoxy. WEST SYSTEM® epoxy is a wonderful material for repairing polyester fiberglass boats. One reason for this is the ability of epoxy to form a stronger mechanical bond to a damaged laminate than polyester resin. Epoxy also provides a better moisture barrier than polyester resin. Continue reading

There Will Be a Test

by Kay Harley

A research mentality and ongoing epoxy testing permeate all levels of Gougeon Brothers, Inc. We are committed to rigorous, long-term research on WEST SYSTEM products and their uses with other materials in wide-ranging applications. Studies include the basic chemistry involved, safety for users and the environment, formulation changes, product modifications such as adding pigments or UV additives, panel strength and stiffness with varying composite lay-ups, and the strengths of epoxy bonds, including hardware bonding. GBI commits capital investments to improve its testing capability and supports active ASTM involvement.

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Swift Solo

Swift Solo

Building for Long-Term Competitive Performance

by Bram Dally

Above: The Swift Solo in action. The complicated rig is designed to be managed by one person while they hang from the side of the boat.

Swift Solo, a single-handed skiff built by Bram Dally.

When Meade Gougeon asked me if I’d write a piece about what I’m up to for Epoxyworks, I was honored. He had read the January 2002 article on my single-handed skiff in Sailing World and offered the assistance of GBI (Gougeon Brothers, Inc.) to do some extensive testing for us on several composite samples. Continue reading

Epoxy’s Adhesion to Wood

Woods of the World Epoxy Adhesion Testing

by Tom Pawlak — GBI Technical Advisor

Above: Epoxy’s adhesion to wood is the focus of this study of dozens of wood varieties from Africa and the Philippines.

We recently purchased a 154-piece wood sampler from Eisenbrand Inc., Torrance, California. The 3″ × 6″ × ½” specimens originated from points all around the world. Each specimen was provided with its common name, scientific name, and country of origin. There were several specimens we’d never heard of in this study of epoxy’s adhesion to wood. Continue reading

Chopped Strand Mat

Chopped Strand Mat and Epoxy

by Tom Pawlak — GBI Technical Advisor

Above: Wet-out chopped strand mat and woven fabric test samples are prepared for moisture uptake testing.

Chopped strand mat, in fabric form, is sold on the roll and in small folded packages. It is made up of 1″-2″ long fiberglass strands that are randomly oriented and typically held together with a styrene-soluble binder that acts like glue connecting the fibers. The binder is designed to dissolve upon contact with styrene in polyester resin or vinylester resin. Once dissolved, the fabric softens, allowing it to drape around curved shapes. It comes in a variety of weights between .75 oz to 3 oz per square foot. The most popular weights are .75 oz and 1.5 oz. Continue reading

Epoxy Adhesion Over Stains

by Tom Pawlak — GBI Technical Advisor

Above: Testing of epoxy adhesion over stains was done with a number of different stains.

We have occasionally reported results of adhesion testing of WEST SYSTEM® epoxy to wood coated with various stains. In “Varnish Over Epoxy,” we touched on the topic of wood stains under epoxy and warned that some oil-based stains would cause an adhesion problem for WEST SYSTEM Epoxy. Since then, we have done some additional adhesion testing of epoxy over a number of stains. Continue reading

adding pigments to epoxy

Adding Pigments to Epoxy

by Bruce Niederer — GBI Technical Advisor

Above: Our study of adding pigments to epoxy.

We often get asked ‘What can I use to color my epoxy?’ The intended application is as varied as our customers. Often it’s simply to make it easier to paint over or to provide a color indicator between layers. Sometimes it’s to match a particular colored material in a repair. Maybe it’s for an art or craft project. The point is, people are often looking for a color other than the black 423 Graphite, 501 White or 503 Gray Pigments offered in the WEST SYSTEM® product line. What are some options for adding pigments to epoxy? And what are the pigment’s effects on the performance of the epoxy? Continue reading

A great tool when you want to prepare fiberglass laminates for epoxy adhesion

A Better Way to Prepare Fiberglass Laminates

by Tom Pawlak — GBI Technical Advisor

Above: The Rapid Strip Brush™ is a great tool when you want to prepare fiberglass laminates for epoxy adhesion.

During a recent inspirational hardware store visit, I discovered a rotary wire brush made by Norton™ called the Rapid Strip Brush™. It is used with an electric drill and produces results comparable to bead blasting or a needle scaler. The package says it can be used to abrade metal, masonry, and fiberglass. I immediately thought of a fiberglass application that I wanted to try it on. Continue reading