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PMC OneFire Sterling

PMC OneFire Sterling benefits from the same great working features as PMC Flex which allow a much longer working time compared to any other type of metal clay. It is also the only sterling silver metal clay on the market that requires a single firing without carbon on an open shelf. 

Once fired in a kiln, the silver feels very much like traditional wrought or cast sterling silver. It consists of pure silver, binder, water and 4% copper. This means it easily meets minimum UK hallmarking standards for sterling silver (.925) once fired.

PMC Onefire Sterling is ready to use straight from the pack. The clay is grey in colour but this will transform into a bright, white silver once fired and polished. Use Badger Balm or a little olive oil as a release agent for your hands, texture mats and plates. There is no need to use a release agent for your spacers, roller, work surface or moulds.

Clay is easily joined with paste made from the lump clay. It only requires one or two coats to create a secure joint.

Rings should be made 4-5 US sizes larger to allow for shrinkage. However, the increased strength of PMC OneFire Sterling means that they can be as think as 1mm (plus depth of any texture).


The dense nature of the clay means that it requires a little longer to dry compared to PMC3 or PMC Flex. However, in an Excalibur dehydrator (available from the additional drying time is a matter of minutes. If working without a heat source start by leaving your ‘core’ pieces to dry overnight and refine/paste the following day until you get used to recognising when the clay is completely dry.


We recommend using an Evenheat or Paragon kiln. Dry items can be placed in a cold or preheated kiln. Place on a porous kiln shelf and insert into the cold/preheated kiln. There is no need to use carbon. 3D items can be supported on some kiln pillow.

Firing schedule: Full ramp to 900C and hold for one hour. For best results fire between 870C and 900C.  Approx. shrink rate is 15%. It cannot be fired with a handheld torch.

Evenheat Kiln Tip: Create a OneFire Sterling PMC Preset programme by adjusting the PMC Standard (discontinued) programme on your kiln. This is already set for a full ramp to 900C for 2 hours. Use the down button to reduce the time from 2 hours to 1 hour. See The PMC Studio Youtube channel for instructions video.

Once fired, items will look grey in colour. Quench in water (without gemstones).


PMC OneFire Sterling requires minimal polishing. You may wish to give it a quick brush with a stainless steel brush. However, it is easily polished straight from the kiln into a tumbler polisher. You will notice it polishes up in record time. Our tests showed it polished up in 15-20 minutes compared to an hour with PMC3 or PMC Flex.

The resulting silver is whiter and brighter than PMC3 and PMC Flex and more akin to wrought or cast Sterling Silver.


  • Considerably stronger than any other type of PMC; feels and handles like wrought or cast sterling silver
  • Brighter, whiter silver once fired compared to PMC3 and PMC Flex
  • Long working time; in tests we rolled the clay 15-18 times without cracking
  • Easily made into smooth paste – ideal for leaf and organic painting projects
  • Joins with minimal effort
  • Firmer texture compared to PMC Flex means it is easily manipulated/sculpted by hand and cut without dragging using a needle tool or safety cutter
  • Takes great detail – ideal for fingerprint jewellery
  • Easily carved
  • Can be combined with PMC3 Syringe and paste
  • Smooth texture of the clay means much reduced refining/sanding is required
  • No firescale (no need to place in safety pickle or Picklean)
  • Quickly polishes up
  • Takes antiquing solutions, such as Platinol well
  • Easily soldered
  • High silver content means it easily meets UK hallmarking standards for sterling silver

PMC OneFire Sterling vs PMC Flex

These products are like brother and sister in their handling ability. Each has its unique qualities.

Use PMC Flex for mixed media. The lower firing temperature and consistency of the clay makes it ideal for combining with glass, ceramics and gemstones. It is also good for creating fine or small elements that need to remain flexible whilst being used. The consistency of the clay makes this slightly more pliable.

Use PMC OneFire Sterling for items that need to be extremely hardwearing such as fingerprint jewellery, rings and paste projects. The slightly firmer (though not drier!) consistency compared to PMC Flex, means that the inside of rings are considerably smoother and rings keep their shape whilst being made.