Saturday, 14 April 2012

Conditioning a scorifier and melting a small amount of scrap

This post has been prompted by a question on a jewellery forum I haunt :0)

So I thought i would put together a brief "how to" on conditioning a new scorifier and a short video of the process of melting a small amount of scrap silver. The idea of the video is to show the length of flame, intensity, angle and so on. 

Things you will need:

Scorifier (in this instance it is a 2" square ceramic)
Tongs/handle    (to hold the scorifier)
Torch   (I am using an oxy/gas unit which can be seen in an earlier post about casting into cuttlefish bone)
Borax powder
Mould  ( I use a piece of wood with a dent in it, which has been scorched with a torch to prevent the wood catching fire, other moulds can be ingot moulds, which are the ideal thing but due to their weight I have not bought as the postage to me here in France is prohibitive for something that I would use infrequently, or a cuttlefish bone mould; see earlier post  http://kwantessentials.blogspot.fr/2011/01/casting-silver-in-cuttlefish-bone.html , water casting or delft clay).
Soldering block or some other heat proof item to lay the scorifier on to cool once you have finished.

When first you receive a ceramic scorifier, the surface is matt, this needs to be treated or "conditioned" to allow your scrap metal too melt and pool freely in the bowl. In effect what you want to achieve is a glazed interior surface.

Well used with glossy borax coating and a new one untreated.


To do this, have to hand some powdered borax, or if like me, chip bits off a borax cone and grind them in a mortar and pestle till you have a powder. Mix a little of the borax with some water to make a paste and paint it on the inside of the scorifier, (you can just use the dry powder but it tends to expand and float off or get blown about by the flame so a little dampness keeps it in place).

Next fit the handle to your scorifier, making sure it is tight but too tight and that the pouring lip is to the side for future use. ( I know some people have had difficulty when they first get this type of handle, I did too and ended up having to ring the supplier to find out how the thing worked, ha, well I was told that they supply it with the spring part fitted to the wrong side for easier packaging, all made perfect sense after I put it on the correct side duh )

Light your torch and with a strong bushy flame heat the scorifier keeping the flame moving, till you see the borax melt, tilt the scorifier in a circular fashion to spread the molten borax round the interior of the bowl. At first it will be patchy, and you will not cover the entire surface of the bowl. The process will have to be repeated either by adding dry powder to the now hot bowl, or letting it cool and painting on some more paste. Do this until you have an even glossy coating on the inside of the bowl. Do it gradually, you do not want a thick coat, as over time and with the addition of more borax when smelting it will build up and eventually need to be melted on its own and any excess molten borax poured out and disposed of, if this is not done at some point you will be pouring molten borax and metal at the same time   and they will stick together, not a serious problem as it can easily be rectified by remelting, but it is a pain.

Now to melting your scrap: select the pieces of scrap you want to recycle, making sure it is clean and free from debris. Squash larger bits of sheet with pliers if you can so that the scrap is in a close pile. The two nuggets resulting shown below are 8 and 7 grams just to give you an idea of quantities, I have melted more in this size of scorifier but that is all I had at hand for the moment. Once melted it reduces in volume so a little more scrap can be added to the pool of already molten metal, rather than trying to cram the scorifier full at the beginning.



Two notes on above video, you will not see me adding any borax to the melt as I sprinkled a pinch on before the camera was switched on ( not enough hands :0)  ), as the borax melts along with the metal, the metal pools on top of the molten borax. Once the metal is molten, not seen in the video because of the flame, you will see on the surface of the metal a kind of film/scum. Keep the flame on the molten metal for a couple of seconds and let this film roll away from you as it is this film that is caught in the molten borax and helps to skim off impurities.

It is best to keep a separate scorifier for each metal you wish to melt, fine silver, sterling, gold.


The resulting lump can now be hammered out on an anvil to the desired shape and thickness, or if you have used one of the clamp type ingot moulds and are lucky enough to have a rolling mill, rolled out.

Fine silver on the left and sterling on the right.





All photos will enlarge for clearer viewing if clicked.

5 comments:

  1. Interesting! Lots of heat there -can you quench the metal or just let it cool completely on the board? Thanks for sharing.

    ReplyDelete
    Replies
    1. Hi Lisa, yes you can quench it straight away or leave to air cool as you wish. Then for hammering or rolling out just anneal as you would normally do.

      Delete
  2. Hm.. On the last picture. Didn't you mix up the left and right?
    Fine silver on the left (not right) and sterling on the right (not left).
    Anza

    ReplyDelete
    Replies
    1. Yes I did thank you I have now corrected it.

      Delete
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