Trade Secrets: Additive of the Month – March 2019
What is it? WEST SYSTEM® 423 Graphite Powder has specialist applications. The material consists of a very finely ground graphite, an odourless mineral that is widely used in paints and lubricants, so is readily available and inexpensive.
Used for? When mixed with WEST SYSTEM Epoxy, 423 Graphite Powder adds a natural looking grey/black colour to mouldings and other cast items. When applied as a coating, 423 provides a low friction surface, so tends to be used as a bottom ‘paint’ on dry-berthed sailing craft and powerboats. Graphite Powder is also used as a coating for rudders and centreplates and to bond teak decks where it is squeezed out into the gaps to help with the decorative finish to the seams. The material is slightly electrically conductive and can obviously get hot in the sun, although it also helps protect the resin from UV damage.
Mixing ratio? Graphite Powder should be mixed at a ratio of 10% by volume.
Wessex Resins and Adhesives’ Technical Advisor, Hamish Cook says: “423 Graphite Powder is a very versatile additive and due to its low friction properties is particularly good for making rudder bearings. If kept dry it has a very long shelf life and can make mouldings look great.”
To get the best results, Hamish says:
Keep your powder dry
“Like all powder additives, store 423 Graphite Powder where it can be kept dry. Our containers are made of plastic, so unless you leave the lid off during a shower the contents should stay highly workable.”
Work clean – don’t smudge
“As we all know from pencil sharpening, graphite is easily transferred on fingers and implements, so just be aware that this powder marks porous surfaces very easily. Take extra care not to let the powder get airborne and land on clean surfaces.”
Use the right co-additive
“When laying down teak decks, a thickened epoxy/423 Graphite Powder mix produces the ideal bonding agent as it can also fill the seams. A thickened epoxy is made with 404 High Density filler or 406 Colloidal Silica and then darkened down by adding the Graphite Powder. However, avoid using a fibrous additive like 403 Microfibres. The strands can break the surface and appear as thin white lines in your otherwise perfect black seams.”
“When making an epoxy mix of 404 High Density Filler and Graphite Powder for deck seams, establish the right ratio of each additive for the best look and then rigidly stick to it. The ratio is best calculated by the weight of each component. Rigidly stick to that ratio when mixing every subsequent batch. This will give you perfectly matched deck seams throughout the project.”