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Instructions for the use of Metallic Jewels in G.R.P. Mouldings

The most attractive appearance of Metallic Jewels is when they appear to glitter from behind a shiny glass-like surface, with a completely random orientation of the individual particles. It is therefore preferable to have a very good finish in the working mould to help obtain the best surface gloss on the resultant moulding.
A thin layer of clear, unpigmented gel coat should preferably be applied evenly to the mould and allowed to cure. The more evenly it is applied, the better. This gelcoat helps to provide a deep gloss, and in applications where cost is critical, can be dispensed with, although a less impressive finish will be obtained. The Metallic Jewels are then mixed into a further clear thixotropic gelcoat resin, at a loading of around 12.5% by weight (i.e. 1lb Metallic Jewels per 8lb of gelcoat). This gelcoat should be applied to the mould in such a way that the Metallic Jewels are evenly distributed. Certainly the best (and quickest) method is spray application, but if no spray equipment is available, the gel coat can be 'stippled' on, taking care to ensure that the particles are distributed in such a way that they do not follow and hence show up brush marks. It is worth mentioning that if this coat is applied by brushing in the normal way, the Metallic Jewels will lie down in the direction of the brush movement and the resultant colour effect will be comparable to that of a grass lawn mown in different directions; the 'stippling' is therefore necessary to destroy this effect which would give a very false and unpleasing finish.
The gelcoat thixotropy is important to hinder settlement of the Metallic Jewels and avoids 'runs'.
Nevertheless, the Metallic Jewels may still settle in the mixing pot, so regular stirring is necessary. When applying by a spray gun which has the resin pot mounted in the gun, two ball bearings dropped in the pot will maintain dispersion if the gun is shaken regularly during application.
When the Metallic Jewel coat has been applied and allowed to cure, lay up can proceed in the normal way. However, the laminating resin should be pigmented in a colour to match the Metallic Jewels in the gelcoat. This pigmentation is important, and provides a 'back-up' to the Metallic Jewels in the small areas where the Metallic Jewel particles have not given coverage (namely, between the individual particles).
An exact colour match for the laminating resin pigment is unnecessary (and anyway, virtually unobtainable). If, for instance, Royal Blue (15E) Metallic Jewels are used, a blue pigment should be chosen for the back-up resin, in a colour as near to the Metallic Jewel Royal Blue as possible. If a choice has to be made between a paler blue than the Royal Blue (15E) or darker than it, the darker one should be used, as this causes the Metallic Jewels to 'stand out' better. It is not necessary to use polychromatic colours for backing-up in the laminating resin. The leading suppliers for polyester pigment pastes can normally recommend a suitable colour to match Metallic Jewels.
Should any difficulties or queries arise, do please contact us, when you can be assured of our very best attention and efforts to assist.
N.B. Our Polycon Gelcoat Spray Gun is particularly well suited to the application of metallic jewels. Please see page number 10 for details.