Sentence:  An <WSD>underfired</WSD> or short-fired piece is likely to break if you attempt to change its shape because it is built of many small particles of silver, joined together at the edges. A properly made, fully sintered and fully annealed metal clay piece should be able to stand up to any traditional metalsmithing technique. 
Meaning of the word marked with <WSD> tags:  Fired at a low (or excessively low) temperature.