The technique of moulding glass fibre reinforced plastic is to achieve a composite material, comprising layers of minute glass fibres enclosed in a rigid plastic layer. These glass fibres act as reinforcement within the plastic (polyester resin), very much as steel bars act in reinforced concrete. The process involves thoroughly impregnating with liquid resin, layers of glass fibre, into pre-conceived shapes. A chemical change then takes place due to the inclusion of a hardening agent (catalyst) in the resin, and the material sets into a rigid laminate. All glass fibre moulding work is a variation on this simple, theme.


Ideally, the working conditions should be warm and dry, but it is essential that there is adequate ventilation. Damp and cold conditions will inhibit the cure of the resin.


The items normally associated with glass fibre mouldings such as boats, car bodies, motor cycle fairings, have all been produced from a mould. This can be made of many materials, hardboard, timber, aluminimum: or a combination of these. Where a production run is envisaged, the mould is quite commonly made of glass fibre itself, this mould having previously been cast over a pattern representing the shape of the finished moulding.

Having constructed the mould, the surface must be sealed where necessary with varnish or similar material and then flatted down and polished to the required standard.

Of course the handyman's first introduction to glass fibre is likely to be to carry out repair work to an existing moulding, and often a mould will not be required.


It should be mentioned at this stage that the mould will have to be protected with a Parting Agent to present the moulding adhering to the mould surface.


On most applications the smooth moulded exterior surface of the laminate consists of an initial layer of specially formulated resin containing no glass fibre reinforcement, this lover is called the gel-coat. The built-in colour associated with glass fibre mouldings is incorporated in this layer. The object is to back up the, gel-coat with layers of glass fibre reinforcement which are thoroughly impregnated with catalysed laminating resin, all the entrapped air bubbles haying been squeezed out, by use of a laminating roller.

All tools must be washed in cleaning solvent as soon as gel-coating or laminating is finished, before the resin sets on the tools, making them useless.


The cure induced by the addition of catalyst to the resin is a gradual process taking several hours. Do not be over anxious to release the moulding-it is preferable to leave overnight to ensure a full cure.


Glass reinforced plastic can be readily cut and sanded by a variety of mechanical and hand tools.


The glass fibre moulding can be painted if the surface is thoroughly prepared to remove any parting agent, and to give a key for the paint. Must paint suppliers normally give recommendations for painting glass fibre, which are similar to painting metal and other non-porous surfaces.


Resin materials have been specially prepared to enable inexperienced personnel to fabricate a sound laminate or repair a damaged glass fibre moulding with ease.

The materials used in the glass reinforced plastics industry do however present their own problems which must be borne in mind when using them.



Resins, cleaning solvent, parting agents, pigments and especially catalysts, are all inflammable and care must be taken to ensure that they are stored in their own containers in a cool place out of the sunlight and away from any naked flame. Glass fibre reinforcements should be kept thoroughly dry as any trace of dampness in these materials will impair the quality of the finished job.

Resins are chemicals which by their very nature are undergoing a slow, constant and irreversible change from a liquid to a solid. Ryplas resins therefore have a limited shelf life even in their original sealed containers of between three to nine months dependant upon temperature. When handling resins avoid contact with the skin and particularly the eyes. Resin may be removed from the skin with Ryplas cleaning solvent used sparingly. Liquid catalyst must be handled with extreme care as it is an organic peroxide and may cause severe skin irritation.

Eye contact:

Rinse with water and continue this treatment for at least 15 minutes. If possible, alternate rinsing with a 5% aqueous sodium ascorbate solution* or a 2% aqueous sodium. bicarbonate solution*. Do not apply an oil or fat containing ointment. Afterwards a doctor, preferably an eye specialist, must be consulted without delay.

Skin contact:

Rinse with water and wash thoroughly with soap: next apply an ointment such as lanoline.


Drink large quantities of water or take the 5/, aqueous sodium ascorbate solution and try to vomit instantly. Consult a doctor without delay to give an additional stomach wash.

When handling any of the above materials it is wise to use barrier cream and rubber gloves wherever possible.

Glass reinforcement can cause irritation of the skin. Although it is unlikely to have any lasting effect it can be temporarily unpleasant and it is therefore advisable to handle with care and try to avoid the glass fibre from penetrating clothing. If continuous use of the material is anticipated it will be as well to keep a set of loose fitting clothing apart for this purpose. Always work in a well ventilated area. When trimming and particularly when sanding finished mouldings it is advisable to wear a respiratory mask to reduce inhalation of trimming dust.

* Both solutions deteriorate on storage: they must be freshly made every month.