How much catalyst
Thorough mixing of catalyst into resins and gelcoat is very important. Also the correct additions should be observed to maintain good results. Dispensers are advised for accuracy.
The details below gives the correct ratios of catalyst to resin and gelcoat by weight. 1% is considered a slow mix, 2% is ideal, 3% is a fast mix. Additions outside these bands in not advisable for proper curing, in fact adding more than 4% may result in a failure to cure.
The pot life of these mixes is also determined by temperature. The higher the temperature the faster the cure. As a general guide 2% addition at 20ºC gives 15-20 minutes pot life. The resin will always cure quicker if left in a mass such as the mixing bucket or in castings. Never mixed gelcoat or topcoat above 2% it is best to mix smaller amounts frequently.
Follow the basic principles based on weight for example 10kg will use 200ml at 2%
1kg @ 1% is 10ml
1kg @ 2% is 20ml
1kg @ 3% is 30ml
1kg @ 4% is 40ml
Hazards & precautions
Most fibreglass materials are perfectly safe to use, providing the potential hazards are recognised and reasonable precautions adopted. Normally you will have no problems if you follow these simple rules:
1. Do not let any materials come into contact with the skin, eyes or mouth.
2. Do not inhale mists or vapours-always work in a well ventilated area.
3. Do not smoke or use naked flames in the working area.
Skin and Eye Contact:
Many materials used in fibreglass work are corrosive, or have some undesirable affect on the skin. The simple answer is not to allow any materials to come in contact with the skin at all. Plastic gloves and barrier creams should be worn at all times. Catalyst (hardener) used for polyester resins is an organic peroxide (methyl ethyl ketone peroxide) and is particularly dangerous. Use the correct dispenser for measuring, and be especially careful when handling this substance. Take great care not to get it in the eyes or mouth. If catalyst is splashed in the eye, irrigate under running water for at least 15 minutes, whilst summoning medical aid. Acetone and brush cleaner are powerful grease solvents. If these come into contact with the skin, they can destroy the natural oils and may lead to an unpleasant form of dermatitis. For this reason, brush cleaner should not be used for removing resin from the skin. Resin should be removed with industrial resin hand cleaner such as Kleen All paste then wash in soapy water. If polyurethane foam mixes get on the skin, wash off IMMEDIATELY. Once hardened it is difficult to remove. The remeltable flexible moulding compounds also need particular care in handling. Their melting point is very high and, should the molten material come into contact with the skin, severe burns can result. None of these materials should ever be swallowed, nor should they be stored in lemonade bottles or other drinking containers.
Many fibreglass products give off fumes which can be harmful if inhaled in sufficiently large quantities. In normal DIY use, reasonable ventilation of the work area will be adequate. Care should be taken particularly when using polyurethane foam mixes. These produce iso-cyanate fumes during the initial reaction. If overcome by these fumes, the user should be removed to hospital. With most materials, over-exposure to fumes will result in nasal irritation and watering eyes, eventually followed by drowsiness and possible unconsciousness. The simply remedy is to remove the patient to fresh air. If he does not revive at once, summon medical aid. When machining finished items in cast resin or laminated fibreglass, the tiny particles of fibreglass or resin can be dangerous to the eyes and lungs. When filing, sawing or drilling, always wear goggles and a respirator/face mask.
Many resins and associated products are either inflammable, or contain inflammable additives. Styrene (used as a thinner in resins), catalyst and acetone (brush cleaner) are particularly dangerous. Do not smoke or use naked lights, oil burners or similar heating devices in the working area. If a fire does start, do not attempt to put it out with water. Dry powder extinguishers can be used on accelerator, polyurethane foam, mould cleaner, acetone, resins and release agents. The only exception is catalyst, this must be extinguished with water. Fires can be started if catalyised, but uncured, resins are thrown away. The wasted resin will continue to cure and the heat generated by the curing process can ignite other waste materials. Leave unwanted resin in a safe place until it has cured. It can then be discarded without risk.
Generally speaking, small spillages of resins, etc. can be absorbed in sand or earth and thrown in the dustbin. Catalyst is an exception, this should not be mopped up but diluted with large quantities of water. By far the safest procedure to is to take every possible precaution against accidental spillage’s happening in the first place.