Calculating Glaze Melting Points

Triggered by this blog post by Daniël Bende: Arriving at Glaze Temperature
The Glasurenspiel software is no longer available as it was for DOS, and the author is dead.
None of these are hugely accurate, but they may be useful for guidance.

Martin Lengersdorff's flussmittelfactor F

First mentioned in his book "Practical Berechnung von Massen und Glasuren", printed in 1964.
A flux factor, F, is applied to each of the oxides, in two groups X and Y, as per the table below:
X

Oxide	f
Al2O3, ZrO2	0.32
SiO2, TiO2	0.38

Y

Oxide	f
MgO	0.54
CaO	0.58
BaO, CoO, CuO, FeO, MnO, NiO, ZnO	0.60
Fe2O3	0.70
K2O, Na2O	0.88
B2O3, Sb2O3	1.00
PbO	2.00

Using molar representation,
Y = 𝛴(fi.Si) for oxides in table Y
X = 𝛴(fi.Si) for oxides in table X
where fi is the flux factor from the tables, and Si is the quantity. Not sure if the quantity is UMF or molar
F = 100.Y(X+Y)

One source gives firing temperature FT = (161.21789 - F)/0.10252 °C

Another says to use this table, for different glaze types:

Firing temperature	Wall tile	Sanitary	Porcelain	Matt	Crystalline
1000			57	70	82
1020				68	80
1040			55	66	77
1060				64	75
1080			50	62	72
1100			49.2	60	70
1120			47.8	58	67
1140				56	65
1160			46.1	54	62
1180				52	60
1200	45.7	46.7	48.7	50	57
1230		43		48	54
1250	38.9	39.2	41	46	52
1280	35.4	37		44	49
1300	33.8	35.5		42	47
1320	31
1350	28.8	33.8
1380	31
1410	29.2
1435	26.6
1460	24

The table above wasn't formatted so I've done my best to put the right numbers into the right columns.

Sources: https://wiki.glazy.org/uploads/short-url/fzJbamtAOL64DxEVFpvgAZRfJEz.pdf
http://www.potters.org/subject39174.htm