Guesswork so far, but charge in this sort of context is "filler", something that "bulks" out the product (even if that is not the (only) purpose here).

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Note added at 33 mins (2010-03-28 11:29:16 GMT)
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Quite possibly metal powder, though depending on particle size I'm not sure this would be shiny.

Resin FILLER POWDERS for use with Polyester, Polyurethane and Epoxy Resins. Use to achieve effects and pad out your resin to make it go further and reduce ...
www.tomps.com/shop/-c-23.html
We stock a wide range of fillers from basic padding fillers like Fillite or BLR2 through to SPECIALITY FILLERS LIKE METAL POWDERS, Cab o Sil and Glass Bubbles. Each has its own properties and uses but primarily:
• Fillite - Will lighten your cast and pad out resin to make it go further
• BLR2 - Will improve brittleness, surface durability and pad resin out but without impacting on viscosity
• Glass Bubbles - Will lighten your cast to the maximum but will also improve water resistance and surface durability
• French Chalk (Talc) - Will thicken resin rapidly making an easy sand filler for composites
• METAL POWDERS - Will allow you to make items in plastic that look like metal
http://www.tomps.com/shop/-c-23.html

METAL POWDER [Metal Powder] £9.78



500g Lot metal Powder. Available in brass, aluminium, bronze, copper, aluminium or iron. please place your selection in checkout notes.

http://www.tomps.com/shop/metal-powder-p-229.html?osCsid=5mm...

The metal content of the METAL / RESIN MIX should be as high as possible; too little METAL FILLER is as bad as none at all. Cold Cast Resin Metal pieces in ...
www.tiranti.com/subdivision_product_list.asp?Subcategory=58...

ISO 14001 certified manufacturer of METAL POWDER FILLER for plastics. ... A wide variety of polypropylene & polyethylene neat resins are also available. ...
www.thomasnet.com/.../plastics-fillers-28590404-1.html


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Note added at 5 hrs (2010-03-28 16:38:58 GMT)
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CHARGE métallique n.f. Poudre de métaux (laiton, bronze, étain, aluminium) qui est INCORPORÉE DANS DE LA RÉSINE pour lui donner, lorsqu'elle a durci, un aspect et une densité rappelant le métal.
http://www.nella-buscot.com/lexique_c.php

tu veux que ça ait un ASPECT MÉTAL tes os ? si oui tu peux ajouter de la CHARGE MÉTALLIQUE (aluminium par exemple) en proportion 10 volume (rectification 10 fois le poids) pour 1 de résine (ou de gel-coat).
http://www.trollcalibur.com/phpbb/viewtopic.php?f=92&t=2798

Une RÉSINE SYNTHÉTIQUE, de même nature chimique que les adhésifs, mais comportant une CHARGE MÉTALLIQUE a été sélectionnée pour la réalisation des morceaux manquants. [missing metal parts]
http://www.lrmh.fr/lrmh/w_publications/metal/ptaterb.html

La RÉSINE, DANS LAQUELLE EST INCORPORÉE UNE CHARGE MÉTALLIQUE ou de la poudre de marbre, est souvent utilisée pour le tirage d'une SCULPTURE à partir d'un ...
www.nella-buscot.com › ...


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Note added at 9 hrs (2010-03-28 20:18:46 GMT)
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One example is Cycoloy EF resin from GE Advanced Materials Plastics, Pittsfield, Mass., an ENGINEERED RESIN METALLIC FILLER THAT CREATES A SPARKLE EFFECT.
http://www.appliancedesign.com/Articles/Materials_and_Joinin...