Materials for making dams

Rectangular or straight sided shapes

Broken shelves

Accidents happen to mullite shelves causing breaks or cracks.  Rather than throwing them out, you can cut them into rectangles or 50mm strips with a tile saw.  The resulting shapes need to be kiln washed to keep glass from sticking.  They can be used flat or stood on their edges with supports on the outside.

Thick ceramic tiles can be used in much the same way.  You do need to remove the glaze from the tile to make sure they don’t stick to the glass.  Or you could use the unglazed side toward the glass. Again, the tiles need to be kiln washed.

Stainless steel can be used as a dam.  It will need treatment with a separator such as boron nitride or kiln wash.  In addition, it needs to be lined with refractory fibre paper to cushion the force of the greater contraction of steel than glass.

These materials cannot easily be adjusted in length to fit the size of the glass piece being dammed.  Instead, arrange them in a swastika like formation. 

This photo also shows how shorter lengths can be incorporated to make the whole dam.

Vermiculite board is a refractory material that can be used to form dams by cutting with a wood working saw.  The saw you use to cut the vermiculite will be dulled and only be useful for cutting vermiculite in the future.  Do not use any expensive cutting equipment!  

Credit: Bullseye Glass Company

Refractory fibre board is available in many thicknesses.  It can be cut with craft knives even though it dulls the blades quickly.  The thicker boards can be used without rigidising.  This avoids the need to kiln wash and allows adjustments in length.  If you do rigidise fibre board, you must coat it with a separator such as kiln wash or boron nitride.

Weighted fibre paper can be used.  It is sometimes the quickest and easiest to use, as there normally is a stash of scraps around the studio.  It is easily cut with a craft knife.  You can build up the thickness of the dam by layering pieces on top of one another.  Sometimes people put metal wire or pins in the layers to ensure there is no movement between the layers. I’ve found that if weighted, the fibres interlock enough that the layers do not shift.  But you need to line the layered fibre paper dams with vertical strips of fibre paper, so the glass does not take up the layered dam profile on its edge.

Note that you need to use breathing protection when cutting all these materials.

Curved and circular pieces

Many times, the shape to be dammed is not formed of straight lines.  Different materials need to be used in these cases.

Formed stainless steel is a good durable and reusable material.  You need to line the shape with fibre paper if it completely contains the shape, because it contracts more than the glass and can crush the piece.  It is expensive to have made and so needs to have multiple uses to justify the cost.  A cheaper alternative is to make your own shape using stainless steel strapping as used for shipping crates and pallets. 

Fibre paper is an excellent material for damming irregular shapes.  It can be cut into complicated shapes, and it can be layered to attain the required height. You can weight it if you are taking things to a high temperature and fear that the glass will flow under the fibre paper.

You can also use the thicker fibre papers upright by backing up with multiple pieces of kiln furniture to maintain the shape you desire.

Vermiculite board is a good material for making shapes, although not as complicated ones as possible in fibre paper.  Vermiculite can be shaped with wood working materials, but cheap ones should be used as they are quickly dulled. You can rough out a shape with a jigsaw and refine it with various wood working tools, including coarse sandpaper.  Because it is a relatively rigid material, a lot of inventiveness can be used in forming the edges by altering angles from the vertical, incising designs into the edge, etc.  Be certain that you have adequately kiln washed or put other separator on the board, as it will stick to the glass if left bare.

Fibre board is a less rigid material than vermiculite, but is easier to work with simple craft tools.  It is simple to use for a unique one-off shape. It only needs smoothing and does not have to have a separator applied because it does not stick to the glass.  If you create a shape that you will want re-use, you can rigidise the board after shaping, but it will require separators then.

Note that when working with refractory materials, you need to wear respiratory protection and clean surfaces with a HEPA vacuum or by dampening dusty surfaces and wiping them clean.  Dispose of cleaning materials safely.