Suitable fibreglass is placed in the lower half of the mould and the flowing polyester is distributed. The mould is closed and the polyester impregnates the fibreglass material. The press pressure is low and, therefore, moulds made out of fibreglass can be used.
There are several methods of pre-moulding the fibreglass material before it is placed in the mould. Fibreglass with a thermoplastic binder is frequently used, whereby it is heated, pre-moulded and cooled. It can then be placed in the mould.