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Resin to Fibreglass Ratios

For an effective fiberglass laminate, it is essential that the fibreglass material is thoroughly ‘wetted-out’ with Lay-up Resin (Resin A).

The amount of resin needed to do this varies from one fibreglass material to another. The following table shows the amount of Resin A needed per square meter of material.

You can now use our Materials calculator to automatically work out your quantities for gelcoats, topcoats, resin and matting.

Material Spread Rates
(Note: CSM = Chopped Strand Mat)

Priming Plywood.
Laminating, for each layer 300g CSM.
Laminating, for each layer 450g CSM.
Laminating, for each layer 600g CSM.
For multiple layers of CSM.
Laminating with Fabrics.
Casting, unfilled. For each litre.


Resin = 500g per m2.
Resin = 650g per m2.

Resin = 1.1kg per m2.

Resin = 1.5kg per m2.

Resin = 2.5 x CSM weight.
Resin = 1 x Fabric weight.
Resin = 1.16kg per litre.



Gelcoating on mould surface.
Topcoating after laminating.


550g per m2.
650g per m2.


Pigment Pastes


Add 10% by weight to Gelcoat


100g per kg




Add 2% by weight to Resin or Gelcoat.


20g per kg


Wax Solution


Add 2% by weight to Gelcoat, to make Topcoat

20g per kg




Add 2% by weight for thinning resin.


20g per kg resin.


2 Part PU Foam


Expands 25 times its original volume.


1kg per cu ft.


PVA Release Agent


On non porous surface


200g per m2.


G4 Sealer


Sealing porous surfaces


250g per m2.


Carborundum Grit


Spread onto wet gelcoat


1.6kg per m2.


Estimating quantities is very simple using this information and a few calculations.

The important information you require is the surface area you wish to cover, expressed as “m2” and the total weight of Chopped Strand Mat(CSM) used, expressed as “grams per m2”.

Calculating Quantities

Example; Area to be covered is 1m2.

Thickness of CSM required is 3 layers of 600g

Therefore, the total weight of CSM = 1.8kg (3 x 600g).

Resin required for this laminate would be 4.5kg (1.8kg CSM x 2.5)

Please note that the information given is as a guide only. Allowances should be made for overlaps and natural wastage.

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