Quote:
Originally Posted by hyperT
OK you can get away with a difference of 4 coe's. In other words 92 is compatable with 96. When a glass company calls their glass 96 coe they
actually mean 92 to 96 it's not a rigid 96 depending on the color etc. To seal a 33 coe boro to an 8 coe quartz glass you need an intermediary or several between both the glasses that will work with either on either end. Graded seals are used mostly in scientific glass blowing for apparatus manufacture. A scientific glass blower would add this technique to his resume. For instance a 33 boro pyrex is rated as 7740 but there are other ratings as well including 7736 and so on down until the correct number is reached to join the two.
There are other problems that may hinder you in joining two glasses together as well. One would be the viscosity of the two glasses. If one melts and flows easily and the other not they may not work together. If you are unsure just do a simple test by joining the two together overlapping the ends and stretching that part of the mix out to a stinger. if parts flake off or the stringer coils up or forms curve they are not going to fuse well. If the stringer stays intact and stays straight then there is a good chance they will.
Or you can just have fun and forget all this tech brew ha ha,Wayne
P.S. Pyrex 7740 was actually invented for railroad train lanterns as it was not subject to thermal shock when being struck by rain.
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Good stuff here. In my experience though, when color manufacturers talk about 96 COE there is a +- tolerance so 92 - 100 is possible. I think this is why there can be issues within a given mfgrs pallette.