17 Jul 2015

Polishing Bonschelle Bronze Metal Clay

One of the enjoyable things about working with metal clay is seeing the transformation from a brown drab looking piece of clay into a shiny, bright decorative object when it's finished. The polishing process can be so transformative.

You can of course not polish your metal clay items and leave them in their natural state after they have been fired. Depending on when you decide to pull them out of the carbon they can take on varying shades due to oxidisation, from reds and oranges through to bright greens, and can be really beautiful.  Here is an example of some our hearts made with Bonschelle Metal Clay that were fired and taken out of the carbon whilst still relatively hot:

Bonschelle Bronze Metal Clay oxidisation and patina examples
Beautiful colours after firing

The colouration will be heavier the sooner they are taken out of the carbon after firing, but this can also result in some black oxidisation, so it's very dependent on timing - it's a good idea to wait a little bit, rather than pulling them straight out once firing has completed. Leaving pieces to cool completely in the carbon usually results in pieces having a more uniform pale terracotta colour which can also be attractive in design projects:

Bonschelle Bronze Metal Clay after firing and cooling
Metal clay piece left to cool in carbon after firing

If you intend to polish your pieces you will probably find it best to let them cool in the kiln (or at least leave to cool in the carbon till that's cool if you have removed the firing container from the kiln after firing) as there will be less oxidisation. 

When polishing you can determine how much of a shine your pieces have by what tools you use to polish. If you want a high shine use sandpaper in increasing grits, for example 400 first, followed by 600, 800 then a fine grit such as 1200. This will give you a mirror finish. If you would like a more satin sheen instead then an electric tool such as a Dremel with radial wheels. If you decide you don't want a satin finish after all then go right ahead and re-polish the pieces with sandpaper as described. 

With pieces that have a raised texture you can get some beautiful effects by polishing with sandpaper which will only reach the raised areas, giving a contrast between those parts and the unpolished recesses: 

Bonschelle Bronze Metal Clay polished raised areas
High polished areas contrasting with unpolished recesses

Polishing with radial wheels will result in recesses being polished as well as raised parts, as the soft flexible spokes of the wheels are able to reach small areas. Because of that they are very good good for polishing detailed work where you want all the little nooks and cranies polished and a uniform sheen.  In addition they will not sand away delicate details.

A video tutorial giving a step-by-step guide to polishing Bonschelle bronze metal clay will be available soon, so do check back - why not subscribe to this blog or our YouTube channel to keep up-to-date with our latest news and tutorials.

Do you have a preferred method of polishing bronze or silver items? Share below, we'd love to hear from you.