You can slump only 5cm or so per firing. If so, why don't drop rings fail?
This is really about a comparison of deep slumps and free drops.
· The stages of a deep slump give more control of the design
· The shape of the result is determined by the shape of the mould
· The wall thickness will be much more consistent
· For its size the deep slump is lighter than the drop.
· The multiple stage deep slump is designed to have the minimum of cold work.
Single Stage Slump
· If you attempt to do a deep slump all at once you run the risk of ruffle around the upper edge.
· There are likely to be a large number of stretch marks on the outside.
· The design will be distorted to varying degrees along the surface.
· The wall thickness will vary greatly.
· You lose the advantages of the multi-stage slump without gaining the advantages of a drop vessel.
Drop Ring Vessels
· The glass thins as it stretches through the ring, so you need to start with a much thicker blank than slumping.
· There will be a thick base in relation to the sides.
· The design will stretch, and if properly designed will be very pleasing.
· The walls of a drop vessel will vary from thick at the bottom to thin at the top.
· The collar needs to be cut off the vessel and cold worked to smooth.
· The process of falling through the ring needs to be monitored to avoid an excessive drop causing distortion or an insufficient drop causing the need for grinding a flat base for the vessel.