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Rusty's top tips on“How to use”    

Epoxy Mastic 121

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Epoxy 121 is a two pack modified epoxy high build coating.

Comprising of base colour component A, and an equal amount of hardener component B.

Mix components A and B together in equal amounts ie 100ml A to 100 ml B by measure. Allow to stand for approximately ten minutes to allow the chemical process to start.

All of the data on our technical data sheets are calculated at 23 degrees C if the ambient temperature causes the Epoxy 121 to be a higher temperature the product will be thinner. At low temperatures 8 degrees c the product will be much thicker almost paste like.


Epoxy 121 can be thinned up to a maximum of 15 – 20% with the thinners provided in each kit. For spraying or fine brushing you will definitely need the thinner.

" Top Tip" As a surface filler

Without thinning EM121 can be used as a filler coat for imperfections on steel surfaces of up to .5 of a ml thick ( 500 um/microns) by mixing equal amounts of component A and component B without adding any thinner, allow to stand for ten minutes and then brush onto surface and scrape away excess to level the surface.

For Brushing

Depending on the temperature at the time of application Epoxy 121 can be easily brush painted. The addition of up to 15% of the thinners supplied may be added. Use a fully loaded wet brush and long strokes for the best finish.

By Roller

Epoxy 121 can be applied by roller, load the roller up fully before applying to the surface.

Roller application requires twice the amount of coats to eradicate the chance of any misses ( holidays) in the coating.

By Air Spray

Use a spray gun with a 1.8 tip size smaller tips can be used on gravity fed spray guns. Thin the product up to 15% with the thinners provided.

Over painting

Epoxy 121 can be overpainted with any paint product. If fully cured ( over two weeks) a light sanding with an 320 grit abrasive will be required prior to painting.

Seam sealing

Apply Epoxy 121 to the bare steel area first, A seam sealer preferably polyurethane can then be applied over the epoxy 121 to seal the seam.

Filling over EM 121

Due to the very hard nature of Epoxy 121 when cured we would recommend a sanding with an 80 grit and filling with Epoxy paste PC-7.

All the best

Rusty wink

These how to guides are not technical data sheets or Health and safety data sheets those can be down loaded from our data sheet page. Any other technical information on drying times etc is available from the data sheet.

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