One of the challenges of hand lay-up process is to obtain the right resin/glass ratio in each application. In order to control the ratio, below methods can be followed;

1. Visual Check:

Visual check provides a good idea about the quality of lamination.

– A laminate that looks very glossy has too much resin.
– A laminate that looks whitish is too dry and resin starved.
– A good laminate should look clear and dull.

With visual check method, of course you will not be able to tell what the exact resin/fiber ratio is but you can tell if a part is too resin rich or too dry.

2. Weighing resin and fiber:

– Weigh the fiber first
– Calculate the weight of resin
– Weigh the resin

In this method, first ratio of resin/fiber should be decided. After that cut the fiber according to the mold surface. Weigh the fibers and divide the weight of fibers by the decided fiber ratio. Multiply this result by the resin ratio and you will obtain the required amount of resin.
For example;
If we want to produce a laminate with 30% fiber content using 6kg glass fiber;
6 kg / 0.3 = 20 kg

20 kg x 0.7 = 14 kg resin
To make sure the calculation is correct;
We produce a 20kg part using 6kg glass fiber and 14kg resin.
6 kg fiber / 20 = 0.3 (30% fiber)
14 kg resin / 20 = 0.7 (70% resin)

3. Ignition Test:

Cut a small specimen of cured laminate size 5cm by 5cm. Weigh the specimen and place it in oven at 700°C for 1-2 hours. By this way, all the resin and organic materials will burn out of the specimen and leave only the glass. Weigh the specimen again. Divide the second weight by the first weight to obtain glass fiber ratio. If the laminate contains gel coat or fillers, the results will not be accurate.