Fibreglassing Guide

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Fibreglassing with Mouldlife

Also known as GRP - Glass Reinforced Plastic

Safety Notice:

Precaution must be taken when working and handling these materials:

Always use COSHH procedures.
Wear a correctly graded respirator mask for vapours, fumes, and dust.
Work only in well-ventilated and extracted environments.
This guide is for information and health & safety only.
Do not use these materials without adequate instruction or supervision.

Fibreglass and polyester resins

Used together to make extremely durable moulds and cores, capable of capturing exceptional detail.

Benefits

Durable
Lightweight
Extreme strength
Exceptional detail
No expansion or shrinkage
can be baked with foam latex

Chopped Strand Mat (CSM)

Chopped Strand Mat is woven strands of short glass fibre, scattered randomly; cross hatching creating a mat for optimum strength when wetting out with resin.

300 CSM

450 CSM

FIBREGLASS VEIL (TISSUE MAT)

Things to bear in mind when working with fibreglass

More catalyst = faster set, less catalyst = more working time

Warmer room = quicker set, cooler room = more working time

Gel Coat vs Laminating Resin

Gel coat: 3-5% Laminating Resin: 1-3%

Gel coat is generally a thicker resin, this is used as the capture layer; picking up all details of the master. More catalyst is typically used in this layer as you'll require much less working time, as it's just as simple brush up.

Laminating resin is a thinner consistency and is used to saturate the matting thoroughly. Less catalyst is used within this mix as you require a much longer working time to ensure each layer of matting is covered.

Tools & Materials Checklist

Gel Coat Process

When using gel coat, weigh out your resin with 3-5% catalyst into a mixing bowl.
Mix thoroughly with your long-haired chip brush and begin to apply to your surface evenly, ensuring the entire area is covered.
OPTIONAL - Once you have applied this layer, allow to go tacky (enough to feel slightly sticky without lifting any materials) before sprinkling an even coating of choppies all over.
Allow to set before following with laminating resin.

Laminating Resin Process

Laminating either on top of gel coat for mould or straight onto object to create hard conforming shell, weigh out general purpose resin with 1-3% catalyst.
To laminate, use the same cleaned mixing bowl and weigh out your resin and catalyst (1-3%).
Mix thoroughly with a long-haired chip brush and coat one even layer of laminating resin on top of the gel coat/choppies.
TO START - Use small manageable squares of tissue mat for your first layer. Utilise the resin you have layered down first, just loosely place these squares over. Once you have a uniform layer, use stipple motions with your chip brush to flatten this tissue mat onto the surface.
Once the tissue is complete, begin to wet the cut up CSM sheets with your laminating resin, and begin to - again - loosely lay within your mould.
Methodically place the mats within the mould, slightly overlapping to ensure no gaps occur.
Once you have covered the inside of your mould with matting, begin to coat these sheets with more laminating resin until fully saturated, using short stippling motions to push the resin through the fibres with your chip brush – this will flatten the mat and allow it to conform around the master and remove trapped air.
Immediately repeat this process for the second layer of CSM.
Your final layer of CSM can again be the fibreglass veil (tissue mat) for a smoother surface due to its extremely fine glass weave.
It's then a case of allowing to set, cure and begin demoulding!

Demoulding

After the full cure and set time, you can begin demoulding. Your approach may be different depending on the mould that you're demoulding from.
Demoulding from a silicone jacket with a hard shell is super straight forward. Remove the hard shell from the silicone jacket and begin to peel-slide away the silicone jacket from your new fibreglass core.
Add the jacket back into the hard shell and you're done!
The fibreglass core you have just created will have very sharp edges. All the exposed, unlaminated corners of the fibreglass sheets will be overhanging and will need cutting away and filing smooth, avoiding splinter from the fibreglass strands.
Mark around the edge of the fibreglass core with a line to follow when cutting.
Using an oscillating multi-tool, follow along the lines you have just marked. Work in small sections to control the line and tool.

PLEASE KEEP YOUR SAFETY IN MIND WHEN USING POWER TOOLS