What is the purpose of a resin filler?
Primarily its to alter the properties of the resin, be it to lighten or increase impact resistance. One sure result will be the reduction of shrinkage, but be aware adding filler can thicken the resin and reduce air release!

In the next sections we address each of our fillers and their basic benefits.

How much filler to add?
It depends on application but a good start point is 1:1 by weight. If this thickens things too much then back off to 2:1 resin to filler by weight etc and work from a starting point. Always weigh and keep a record for your own personal "sweetspot"

Excessive filler use will also increase brittleness so beware of over filling!!

Fillite - Why?
Cheap filler to pad out resin that will improve impact resistance, reduce shrinkage on cure and change the colour to grey.

It will thicken the resin but not as much as Talc or French Chalk and is a good general purpose filler where you may want to lighten too.

Calcium Carbonate - Why?
Again cheap filler, little effect on weight and improved impact resistance. Reduction in shrink once again.

Make sure you buy COATED filler in this case as viscosity is retained to as much as 1:1 !!!!! Again good general purpose filler with low impact on release of air.

Marble Flour - Why?
Give me weight!!! Give plastic a cooler feel!!! Pad resin on the cheap and reduce shrinkage. This is probably one of the cheaper ones about.

Will impact on viscosity, reducing air release so dont overfill

CABOSIL (Fumed Silica) - Why?
If you are laminating on a vertical it will thicken resin without making it too thick to wet the glass. The benefit is a reduction of drainage from the composite.

Doesnt help shrinkage but then thats quite low with composite structure anyway!

French Chalk (Talc) - Why?
Well this one is really for either thickening to reduce drainage in composites, or a dead cheap filler to reduce shrink. It is one of the longest fillers in history and these days with modern fillers should be used for one thing. Home made easy sand filler paste.

Just add more and more and more until you get a mega thick paste. Then catalyse and use like P38 Isopon! Use a touch of pigment so you know when the cat is fully mixed.

Glass Bubbles or Microballons - Why?
These are probably the most expensive and if you go for a branded version like 3m K15 they give half the density of resin! Lighten to the MAX! They assist with shrink and work with polyesters and epoxies alike. If you want a mega light resin mix for use with say RC Planes, dont mess use these with a bit of glass tissue!

They are not too bad on viscosity but again overfilling will reduce impact strength and release but not really used in casting as such. Used heavily in racing yachts to reduce composite weights as much as possible.

Thanks for taking the time to read this section on our Filler Systems. We appreciate your custom and look forward to not only receiving you first order but any subsequent orders you place. You will get the same level of service whether you are making a one off purchase or become a regular customer! All information is supplied in good faith and for guidance purposes. No responsibility or liability for loss or personal injury can be accepted. The products are supplied as fit for the purpose intended.

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TOMPS Online Management Team
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