CLARE HEDGES
FIBREGLASSING
FIBERGLASSING MATERIALS
Gel coat -
2% ratio, in industry different products may use different ratios
Lay up resin - chopped strand matting different weights - bound together by starch
Fine surface tissue - the same as above, but fine and gives nicer finish
Talc- Industrial (naturally occuring stone)
PREPARATION
STEP 1 -
Talc the sculpt before fibreglassing as this will help the resin stick to the surface.
2 layers of matting (ripped not cut as this will make it stronger) are needed for the mould with a third around the edges for support. They will need to be the strongest part as this is where the it is drilled and bolted later on.
Put release agent on all visible plastic
STEP 2
Ratios of catalyst - 1% is considered a slow mix, 2% is ideal and 3% is a fast mix
When the resin is mixed with catalyst it will turn from pink to a butterscotch colour. It is important to mix and not whisk the mixture.
STEP 3
The initial coating is thinly brushed onto the sculpture and is used to pick up the detail. This layer is known as the Brush up layer, detail layer or print coat.
This is applied with a clean chip brush. Ensure that the resin is applied all over the sculpt, into all the detail, in an even layer - not too thick
The resin should then be left between25 - 35 minutes when cold and 10 - 15 minutes when warm. There will be an exothermic reaction - once it is firm, cold and tacky then it is cured. It is crucial that the resin is tacky - this is important so that the next layer sticks to it. It is important not to leave it too long, otherwise it may delaminate and will not work.
STEP 4
To avoid undercuts - catalysed resin is mixed with talc to create a substance known as mud. It is used as a filler and placed around the undercuts - an example of an undercut may be some areas of the nose. Apply this thickly, filling so it stops air bubbles.The Mud is applied after the brush layer but before the glass matting. This step is not always necessary.
STEP 5
The glass matting should be ripped instead of cut, as the fibres created when ripped will overlap and create a stronger mould than if the glass was cut. This is applied with the lay up resin and 2% catalyst (applied in a similar way to paper mache). It is important to be aware of the areas where matting has been applied to ensure it is strong all over.
The more resin on the matting, the more malleable it will be and the easier to manipulate it will be. Stipple the resin on rather than brushing it on. Force glass down to surface comibining the layers together and chasing out airbubbles.
Once 2 layers have been added and a third around the edges for strength, apply a surface tissue layer. This is not critical but is advisable as it gives a nicer finish.
It is important to put gel coat under water after use as it is a fire hazard
When fiberglassing, health and safety is really important. A respirator must be worn at all times and good ventilation is crucial when working with these materials. Fiberglass resin is very toxic in its liquid state - which is why it is impertative that respirator is worn.
Fiberglass can be used as a cast and mold material, as a mold material for baking foam latex as it takes less time than a stone mold. It is lightweight and tough.
After the fibreglass had cured, I drilled 6mm holes in the middle of the keys which I was daunted by as I had not really used a drill before.
Fig. 1
Fig 2
RESEARCH
Fig 3
This page from Todd Debrecini's Special Make up Effects highlights the necessity for care when fibreglassing from a health and safety point of view.
The resin is very toxic in its liquid state - good ventilation is crucial and a NOSH approved respirator must be worn when fiberglassing. The below picture is an example of a re-usable respirator. There are also disposable respirators available.
Fig 5
This is a different ratio to what we use (1:3) and also uses acetone, this is probably as it is a different kind of cap plastic.
I was interested by what zip spray was but this book is American and I could not find what 'Zip spray' is.
It is interesting that she has used spray mount , this may help the cap plastic to stick to the silicone rather than the mould, stopping it from sticking to the fibreglass mould.
Spatola leaves bleeder holes and waits till the silicone bleeds out and then fills the holes with clay. This shows that the mould is completely full of silicone. This is a useful tip.
Fig. 6
This book states the best way to apply the resin is by spraying it however it also says that it must be done with an effective spray gun which is not cost effective for an amateur and is often not even used professionally. Brushing resin is instead the standard for resin application.
Spraying release agent on the mould can be done using a low pressure sprayer.
Fig 7.
Fig 8.
This diagram is really useful for figuring out the time it will take for gel coat to cure and be ready for the next later, dependant on the temperature of the room. For example: at 80'F it should take just under 20 minutes to cure. This is interesting as each time I have fiberglassed, I have been unsure how long to leave the gel coat to cure.
Fig 9.
This diagram states that the hotter the room, the less catalyst is used. This is an interesting point that I had not heard before