In this test the objective was to get used to applying the epoxy in layers to a curved surface, and to observe the transparent qualities of the finished fibreglass shell. Above is the hardened form in it’s mould.
Along the edge of the mould you can see areas where uncoated fibre mat remains.
The initial coat of epoxy is a mix of blue pigment and microfibre dust. An hour later the chopped fibreglass mat is applied with more epoxy on top of that.
You need to be careful to remove air bubbles as shown above. Sometimes this is because there is not enough epoxy to properly saturate the glass mat. Sometimes there may be too much epoxy. In that case the bubble usually appears darker.
A cross section showing the latex release compound and the layers of epoxy and glass.
Ripping the polystyrene foam mould away from the fibreglass casting.
Once you start to rip the polystyrene away it comes off in big chunks.
The final test piece. The light transmits through the material quite well. The dark brown parts are contamination from some dirt on the bench. The line of different colour is where a new mix of epoxy was used. I have stained the whole batch of epoxy to try to minimise the colour difference between batches.