How to Choose a Gel Coat for Your Mold | How to prepare the gel coat to apply to your mold | How to Apply Gel Coat on Your Mold

What factors should you consider in choosing a gel coat?

Gel coats must be chosen that are tough, durable and designed to deliver A high gloss surface is required. The hardness and chemical resistance of these tooling gel coats develop within 24 - 48 hours after lamination and removal of the master. This rapid development of physical properties allows the mold builder to develop the high-gloss, mirror-like finish required in molds.

Tooling gel coats are features that you should consider before you get them

1. Weight.
2. Specific gravity.
3. Viscosity.
4. Brookfield.
5. Thixotropic index.
6. At least the gel coat shelf life should be at least 3 months.
7. Gel time.
8. Barcol hardness should be obtained with in 1 hour

NOTE The above-mentioned properties vary according to the environment we work in, so we should select the gel coat that has the properties suitable for our environment.

How to mix the gel coat to apply to your mould

The mixing method ensures the most uniform properties during the application of the gel coat. Mechanical mixing is recommended and is sufficient to "rotate" the material 10 times. Most common gel coat mixing equipment achieves adequate mixing in less than 1/2 hour. Do not mix the material continuously as this may cause loss of thixotropic properties. If the gel coat is accidentally mixed, hold the material for 2 to 6 hours without concern before application.

How to Apply the Gel Coat on Your Mold

This gel coat should only be coated on properly prepared surfaces. All experienced mold makers Understand that care is required in plug or pattern making to produce a good mold. I suggest applying gel coats in multiple passes of the spray gun to slowly build up to the desired thickness. It is recommended to apply only 3-5 mils with initial passes of the spray gun. The "many passes" technique keeps air to a minimum and results in a A "pinhole and non-porous" image. A film thickness of 20-25 mils is required to achieve this Maximum mold life. Gel coats are fast gel and should be formulated to provide cure time at a nominal 2% MEKP. At the present time I recommend that applicators use "a catalyst that contains less hydrogen peroxide" such as porosity resistance. It is the mold temperature and ambient air temperature, as well as the required material temperature, that should be in the temperature range of 18°C to 27°C for best results. If there are more specific problems you should research. It is recommended that the catalyst concentration used in standard series isophthalic application based tooling gel coats should not exceed 2.5% or fall below 1.8% to retain maximum properties. The recommended range for catalyst concentration in the applied film is 1.8% to 2.2% at 25°C. Under normal conditions the gel coat is ready to "lay up" in 1 to 2 hours. "Time to laminate" depends on room temperature, humidity and air movement, as well as catalyst concentration and film thickness. A minimum wet film thickness of 18 to 20 mils is recommended for optimal concealment, prevention and performance characteristics. These products should not be used when curing may be adversely affected so temperature conditions, both mold and ambient, are below 18 degree.

Safety considerations to be taken while applying gel coat

Tooling Gel Coats are based on a resin that contains styrene monomer, which is a flammable liquid. Keep away from sparks, heat and open flame. Electrical equipment should be vapor-proof and protected from breakage. Styrene vapors are heavier than air and will tend to concentrate in the low areas of molds and in pockets immediately above the floor area. To keep vapors within a safe limit in all areas, adequate ventilation or suction fans should be used that will remove these styrene monomer vapors. All equipment must be grounded - including spray guns and molds. Both the polyester gel coat and the catalyst may cause burns to eyes and skin. Avoid contact with the eyes! Avoid breathing vapors! Gel coat applicators should wear a NIOSH approved respirator effective for vapors, spray mist and dust. In case of accidental contact, remove contaminated clothing and wash affected skin areas with soap and copious quantities of water. Contact a physician if persistent skin irritation occurs. For eyes, immediately flush with plenty of water for at least 15 minutes; call a physician immediately. Wash contaminated clothing before using.