Finishing bronze objects

[Kate Verkooijen]

Hi Jeroen and Neil B.

Do you ever use fine sand as a polishing agent or a fine sandstone block as a grinding surface when finishing your bronze objects?

Kate

[Jeroen Zuiderwijk]

Hi Kate,

Yes, I regularly use sandstone, but more to grind then to actually polish. I use it when I really have to remove metal, to thin down a cutting edge, or to level the surfaces. It's the first step towards polishing, but needs finer polishing steps afterwards, or it looks very scratchy. Loose sand doesn't work, but mixed with clay and dried to near dry (so you get a mirroring surface on the clay when you rub it) works very well, also in corners that are more difficult to reach, as the block shapes itself after the piece your working on. I clay blocks without sand after that to get a finer finish, followed by burnishing either with a very smooth stone, or a smooth piece of bronze, which brings up the shine. There's other means to get even finer polishes (such as charcoal dust f.e.), but I've never gone for the perfect finish yet.

[Kate Verkooijen]

Thanks, Jeroen.

I thought that perhaps sandstone would be too coarse, but for removing 'bulk' metal to finish the shaping makes sense. Interesting that loose sand doesn't work... I guess it's difficult to get it to stay in the correct place and mixing it with clay seems like a good answer to make a solid sanding block that takes on the shape of what you are working. I would never have thought of using a piece of smooth bronze as a polishing tool!

Thanks again...
Kate

[Brock H]

At Sword Festival 2008, I was one of several people who used pieces of the broken mold on a sword. I wet it and used the outside part of the mold on the sword, wiping it clean occasionally. It seemed to do a pretty good job, though Jeroen could better tell you if it works best as an initial, intermediate or finishing step. I suppose it would depend upon what mixture you used to make the mold.

Of course, there may be better ways to polish bronze. I just thought it was an interesting technique, using part of the mold.

[Jeroen Zuiderwijk]

Yeah, pieces of mould are in between sandstone and clay-sand blocks. They can be used too. Generally I don't use them myself though, one reason is that there are sometimes large hard pieces in it, which give deep scratches that are nearly impossible to remove later on. With unfired clay-sand, you press these bits further into the clay, so usually they don't do as much damage.

[Edwin Deady]

Interesting that they used sandstone to polish stone tools back in the Neolithic.
You can still see blocks of Sarson or Grey Wether sansdstone on the Marlborough Downs above Avebury used as polishing stones or polissoirs.

http://www.celiahaddon.co.uk/standing%20st...s/polissoir.jpg

Edwin

[Kate Verkooijen]

Thanks very much for all your very helpful replies. It's interesting that pieces of old mould could be used for this. Perhaps they used sandstone/stone slabs at the beginning of the metal ages if they were used to that way of doing things for the stone axes and switched to using things connected with metal working as they became aware of their potential...?

Kate

[Steve L.]

For "the allmost shiny" finish i use a hematite. (Not the polished one!)