QuestionWhen i pour melted sterling silver in my ring mould, there are bubbles which form under the surface. How can I eliminate these unsightly bubbles?
Answerhello Steve,
first use a debubblizer on your wax that alone will prevent bubbles.alcohol works to some degree but highly inconsistently- buy a commercial preparation, or look up a MSDS on a product and recreate it yourself. Second, if the sterling scrap isn't perfectly "clean"- you have ensured all solder is removed, and used a graphite rod to remove bits of debris that are visible on the glowing ball of molten metal in the crucible, and use a dedicated crucible lined with a good coating of borax, and then during the melt a pinch of boric acid , then pour into a direct casting mould, or in the lost wax method, have thouroughly burned out your mould you will not have the bubbles appear.
It sounds like you are not thouroughly burning out your investment. That is the major cause of that bubbly effect . Orchid at ganoksin.com has just posted a great video series on the method. I suggest you give it a look. All your answers and more, will be there. The recommended products though are left to ones own taste ( in other words don't buy into subtle advertising!)..use what is available to you and at a cost you can afford.Do however, use clean scrap, or a minimum of 50% new casting grain to scrap silver. Use a magnet to insure all ferrous bits are removed and if pouring an ingot heat the mould to prevent thermal shock to the metal and the piece., or if direct casting a ring in cuttlefish, clay, etc, keep the torch flaame on the metal as you pour. Bubbles in a casting are preventable by following the manufacturers instructions for the burn-out cycle in the investment used. It is quite important to remove all air and moisture or you will get an incomplete casting, bubbles, or porosity- all which can be prevented by checking the kiln's temperature and ramping it correctly for the quantity of metal used, or if treeing a casting, a good debubblizer used to penetrate to the depths of the tree, and if casting with stones in place..A good reference is Murray Bovin's titles :Silversmithing for school and home, and casting for the small shop, and Tim McCreights book on Practical Casting and "the COMPLETE METALSMITH"- are must reads for any self taught silversmith.
I know this isn't much technichal information but if you will go to the Orchid forum, the new series , just posted on casting, will answer all your concerns and demonstrate the techniques necessary to getting the mould, or wax properly ready to be replaced with metal that will give you a cleanly finished piece, with little polishing work and deburring after the pour.
Best regards, Ari
