Isophthalic Polyester Fiberglass Resin Kit

Fiberglass Resin Kit


Our Isophthalic Fiberglass Resin is a big step up from our General Purpose with extremely high water and corrosion resistance, and with greater strength and durability. Yes, our Isophthalic is more expensive than our General Purpose, but this spec resin stays affordable, while giving you more value.


Compared to our General Purpose Resin, our Isophthalic polyester is superior in resistance to chemicals, corrosion, water, impact, heat, and has better adhesion to glass fibers. 

*For Drum Quantities – please contact us via our Contact Us page. 


Fiberglass Polyester Isophthalic Resin


FGCI’s Fiberglass polyester Isophthalic Resin is a rigid, medium reactivity polyester resin. With high corrosion resistance, and the highest water resistance of all our resins, this laminating resin is a phenomenal choice for both above and below the waterline. If you are looking for a higher quality resin with greater strength and durability for your finished product, while not going overboard with costs, this is it.


Our Isophthalic resin applications include hand lay up and spray up of boat hulls, building products, car, truck bodies, pipes, tanks, tank linings, road, bridge, industrial floor coatings, and as a tooling resin in building molds.


Compared to our General Purpose Resin, our Isophthalic polyester is superior in resistance to chemicals, corrosion, water, impact, heat, and has better adhesion to glass fibers. 


With thorough and quick wetting of the fiberglass reinforcement, the usage of FGCI’s Isophthalic resin is considerably reduced. This results in the user building stronger and lighter hulls and parts. From actual field figures, savings of 10% and more have been realised, while greater physical strength is present.


Superior sag resistance makes for even and uniform applications of resin. It helps to control cost and produces better workmanship. 


With FGCI, you can rest assured that your batch will be within specs every time, with the same color, viscosity, strength and application characteristics as you would expect from a high quality product. After all, we haven’t been in business for over 60 years without ensuring our quality standards are the highest, and accompanied with the best customer service! 


FGCI’s Isophthalic Resin Offers:


  1. Moderate AFFORDABILITY for above and below waterline!
  2. HIGH corrosion, chemical, water, impact and heat resistance!
  3. FAST wet out and spray up (if spraying, use ⅛” nozzle)!
  4. SUPERIOR sag resistance!
  5. SUPERIOR Flexural Strength for material stability!
  6. SUPERIOR Tensile Strength, higher than competitor’s Isophthalic Resins!

Isophthalic Polyester Resin Kit Additional Info


  • Isophthalic Polyester Resin is a premium grade formulated product. This polyester resin is designed to wet out the glass reinforcement rapidly without drainage and with minimal resin, corrosion and chemical resistant, and highly water resistant.
  • Avoid using this product in direct sunlight.
  • The ideal temperature for use of this product is 77° F. Best results for this product can be obtained at temperatures between 70° F and 85° F, in a clean, dry, dust-free environment.
  • It is not recommended to wet out fiberglass over 1/8” in thickness. Use of more than 1/8” may generate excessive heat. Allow the layer to tack up (but not fully cure) prior to pouring the next layer.
  • This is an economical resin, designed for hand lay up of boats, panels and other industrial fabrication of demanding quality.
  • If sanding is required to apply more fiberglass, use 36, 24, or 16 grit. Low grits will get you deeper scratches to make the new layer adhere better to the existing one. Be sure to clean the surface before applying another layer.
  • To apply gelcoat, prep the surface with 80 grit sandpaper. To apply primer, prep the surface with 220 grit sandpaper. To apply paint, prep the surface with 320 grit sandpaper.
  • If you have any additional questions or need a product for critical applications, please contact Customer Service at 1-888-849-0588.
Catalyst Concentration Chart - Resins and Gelcoat

Isophthalic Polyester Resin Directions:

Materials Needed

  1. Mix & Measure Buckets 
  2. Personal Protective Equipment (PPE) 
  3. Measuring Cups 
  4. Fiberglass Brushes 
  5. Glass Roller 
  6. Mixing Sticks/Power Mixer 
  7. MEKP 
  8. Sanding Aid 
  9. Paint Style Roller (Phenolic Core or Solvent Resistant)


Step 1:

Choose the appropriate volume for your project. The type of fiberglass used will determine the amount of resin needed.


Step 2: 

Make sure to agitate or stir the product thoroughly before use.


Step 3: 

Mix 1 to 2.% MEKP, in resin solution thoroughly. Please refer to the Catalyst Concentration Chart for Quantities.


Step 4: 

Thinner fiberglass can easily be wet through. To thoroughly wet out heavier materials, apply resin first to one side, then flip the glass over to wet out the other side. Use paint-style rollers to distribute resin quickly.


Step 5: 

Roll each layer with a glass roller to remove air. The fiberglass will go completely transparent when it is adequately wet.


Step 6: 

Add Sanding Aid (Product #123833 must purchase separately) to the final coat to allow a full cure and a tack-free surface. Refer to the Sanding Aid Chart for quantities.


Clean Up Procedure:

Cleaning General Purpose Polyester Resin: Use Acetone to clean brushes and rollers. A small bucket of solvent can be used to clean tools.


PLEASE NOTE: This information is provided in good faith and correct to the best of our knowledge. No warranty, guarantee, or representation is made as to the sufficiency of the information for the safe use of the product, nor to relieve the end user of any Federal, State, or Local regulatory responsibility. 

Does this product contain wax?

There is no wax added to this resin.


Can you add pigment to this resin?

Yes, but only up to 3% max by weight.


How long do I have to wait before I can add another layer of fiberglass?

You will have up to 18 hours to apply additional layers without sanding. Once resin has cured completely, we recommend sanding prior to applying additional layers.


  1. Charlie Norris

    “I love fiberglass coatings. They have great products and excellent advice. I'm trying to open a boat repair shop in St . Mary's, GA and my supply WILL come from fiberglass coatings. When I lived in the Fl. Keys for 36 years and worked for a towing and salvage Co for 15 years all our supplies came from Fiberglass coatings. Great service and never were disappointed. Keep up the great job everyone.”
  2. Brian Lewis

    “The staff are very knowledgeable and friendly Have always gotten the right stuff for the right job. Pat,mark,Colby,Ryan your the best. Pat is the walking encyclopedia of FGCI.”
  3. Justin Lammers

    “Been working on a skiff project and using all FGCI products. They came highly recommended by my friends who are boat builders. It is the highest quality resins, glass, and gelcoat for the money. They made it really easy for a newer person to boat building. The customer service is phenomenal and they are always knowledgeable and ready to help with any questions I had.”