The following ideas and techniques of jewellery manufacturing are reproduced by kind permission of Sandra Noble Goss. (These advanced techniques assume that you have basic jewellery and metalworking skills. We offer these technical papers, originally presented as workshops, in a spirit of sharing information. We assume no liability for safety and health issues - those are your responsibility.)

The rolling mill is a machine designed to produce thinner gauges of sheet metal and wire. Most studio jewellers use a hand cranked mill (although automated mills are used as well). Each mill consists of two smooth, highly polished, hardened steel rolls, mounted in the housing parallel to each other. The rolling mill is used for reducing the thickness of sheet metal. The rolls for wire are cut with 'V' shaped grooves arranged in decreasing sizes, allowing for gradual reduction of wire diameter and producing a square cross section of wire. Most studio jewellers choose a 'combination' mill - half of the roll is smooth (for sheet metal) and half is grooved (for wire). This limits the the width of metal to be rolled (averaging about 2"- 2.5"). Basic use and care of the rolling mill is covered in most jewellery and metalworking books.

Metal which is passed through the rolling mill under pressure with another material will become embossed with a pattern exactly the same as the material being used. Any small particle trapped between the metal and roll will 'imprint' on the metal. If you are attempting to roll a perfectly smooth piece of metal, this is not desirable. But the principle can be put to use to create embossed patterns and designs on metal.

The best way to imprint metal is to create a 'metal sandwich' with two pieces of metal (to be impressed) on the outside (the 'bread' in the 'sandwich') and the material being used as pattern between them (the 'filling')

If you wish to imprint on one sheet of metal only, roll the metal together with the imprinting material, using the roll as the other side of the 'sandwich'. This technique is preferable when using expensive materials (gold and sterling) but has it's drawbacks, as there is more possibility of damaging the rolling mills if materials that are two hard are used for imprinting. It is best to make a 'metal sandwich' whenever possible - it produces two pieces of usable, imprinted metal with mirror image imprints (especially useful for earrings, being symmetrical, but reversed).

1. Metal to be imprinted must be annealed, dry and clean. Depending on the use of the metal after being imprinted, you may wish an emery finish or tripoli or rouge polish. Usually the metal that is the pattern (the 'filling' in the sandwich) should not be annealed - if it is hard metal you will get a better imprint and may be reusable.
   
   
2. Pattern imprinted will be a reverse of the design (important to remember if using letters and numbers in the design).
   
   
3. An object placed between two pieces of metal will create a recess in the metal (intaglio; a mechanical 'etching' effect). As the 'metal sandwich' passes between the rolls and is compressed, the imprinting material is pushed into the metal. Be careful not to roll the imprint so that the metal becomes to thin.
   
   
4. Make one pass only! Carefully adjust the gap by attempting to roll the first 1/2 inch (1cm) or so. Trial and error and experience, along with written notes, are all part of this process. Once the correct gap is calculated, roll the whole piece in one continuous roll. Try not to stop part way through the pass.
   
   
5. To emboss: use a plate with negative spaces so that when rolled the metal plates push into the recessed shapes on the pattern.

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