Many people are concerned about the cost of kiln forming, but use fibre paper rather than kiln wash or powders, although it is many times more expensive. This may be a matter of convenience. This leads me to an exercise in comparing relative costs and benefits of various separators.
Separators are essential to keep the glass from sticking to the shelf or mould that supports the glass. There are several forms of separators –
· liquids and
The papers include the very smooth Thinfire and Papyros papers and the rougher papers ranging from 0.5mm to 6mm. All these contain a binder of some kind.
· Papyros, Thinfire
· Refractory fibre papers - .5 to 6mm
These are mainly suitable for flat surfaces.
· Kiln wash – there is a variety. Most have kaolin - china clay - as a binder. A few do not. These you can just brush off the shelf or mould after firing.
· Colloidal Boron Nitride – a popular formulation is called Zyp.
These are suitable for both flat and curved surface applications.
Powder separators include:
· Alumina hydrate
These have applications directly onto the shelf or mould and onto refractory separators. If used between glass sheets as in bending, very little is required. This is similar when applied to existing refractory papers. As a shelf bed, much more is required.
This analysis of separators shows the first choice is about the application, as some are not useful in a given situation. But in all cases, there are choices in what separator to use.
I used a popular UK website to obtain comparative prices for the various materials.
Papyros paper is listed at £18.46. This is enough for 5 shelves at 52 cm sq. The per shelf cost, assuming two uses per sheet, equals £1.85.
Thinfire is listed at £10.16. This is enough for 5 shelves at 52c m square. The per shelf cost, assuming one use, equals £2.03.
400 g Bullseye kiln wash is listed at £3.96. This enough for about 80 shelves at 52cm sq. The per shelf cost equals £0.05.
400g of Primo primer is give as £6.06. This also is enough for about 80 shelves at 52cm sq. The per shelf cost equals £0.075 (i.e., 7 and a half pence).
Boron Nitride enough for about 25 shelves at 52cm square is listed at £63.93. The per shelf cost equals £2.56.
25kg calcium carbonate is listed at £14.61. This is a one-use material. Applied at half a centimetre thickness, it is enough for 700 shelves at 52cm square. The per shelf cost is £0.02.
300gms talc is listed at £2.99. this is enough for 8 shelves. As this is a multi-use material, assume 10 uses. This gives a per shelf cost of £0.035.
Alumina hydrate is listed at £9.99 for 500gms. Again, this is a multi-use material, so assume 10 uses. This gives a per shelf cost of £0.04.
Ratios of cost between the least and most expensive (given the assumptions) is as follows:
· Chalk =1
· Talc = 1.75
· Alumina Hydrate = 2
· Bullseye shelf primer = 2.5
· Primo shelf primer = 3.75
· Papyros fibre paper = 92.5
· Bullseye fibre paper = 101.5
· Boron Nitride spray = 128
This illustrates that convenience most often wins over expense, as the boron nitride, Papyros and Thinfire seem to be the most popular separators.