Hand Lay-up of Glass Reinforced Plastic (GRP)

The easiest method of making a GRP product, e.g. a canoe is to use a mould.  The mould may be made of GRP or it may be made from another structurally strong material.

The mould is first checked for defects, any scratches etc. are filled. The mould is then polished with a wax polish to a very smooth, high quality finish.  Next, a very thin film of a liquid release agent is applied.  The wax and the release agent are there to prevent the glass fibre product from sticking to the mould.

A layer of resin mixed with a pigment is then applied all over the inside of the mould.  This layer is known as a gel coat.   When the resin has cured, a layer of reinforcing material is laid inside the mould and a measured amount of polyester resin is stippled and rolled into the reinforcing layer.  This layer is also allowed to cure.  More layers may be applied until the required thickness is achieved.  When the product has fully cured, it may be removed from the mould.  The coloured gel coat that was on the inside of the mould is now the exterior covering of the GRP product.  Any blemishes in the mould will have been reproduced in the finished moulding.