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  #26  
Old 10-25-2019, 04:16 PM
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Pete VanderLaan Pete VanderLaan is offline
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what did the simple pull test show you?

I do not like that silica content.

Go back and re read this entire thread. It my help.
http://talk.craftweb.com/showthread....rossphate+opal
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Old 10-25-2019, 05:08 PM
Josh Bernbaum Josh Bernbaum is offline
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The simple pull test showed that the phosphate white was higher in expansion than the SP clear. It bent toward the white a decent amount I'd say.

Here's a formula posted here by Dave in 2016:

Sand 97.5
Soda 36
Lime Hyd. 5.5
Strontium 9
Zinc 3
Borax 9
Alumina Hyd. 4.5
Lithium 1
K Nitrate 1
STPP 6.5

Mine is very similar to that, just put in some K carbonate instead of some of the sodium carb. I calculated his percentage of sand at 56%, by dividing 97.5 by the total weight of 173. But maybe I'm going about that percentage calculation totally wrong, because I see Dave listed the SiO2 content of the above formula at 65.32%. I'm guessing that's more in the range of what you'd like to see for sand content. If Dave is correct on that, then that will be very similar to where my sand content is at as well.
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Old 10-25-2019, 05:16 PM
Josh Bernbaum Josh Bernbaum is offline
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In fact I just checked on your spreadsheet and the silicon % of my mix is 64.94%. I don't know what I did wrong with my division and what I thought was more like a 55.4% sand content. Maybe I'm just calculating weight percentage and not thinking hard enough about oxide percentages which the spreadsheet seems to be accounting for?
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Old 10-25-2019, 06:43 PM
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I'd say, get back to basics.

64% silica is low and it would benefit from better durability even though one can make the argument that Phosphorus is a network former.

If you can work at getting rid of calcium, and boosting other stabilizers at that moment, then look to Strontium and zinc.

I continue to not like borax. If I was trying to lower melt conditions, I would head for nitrates. Lithium is really expensive. Sodium is certainly cheaper than other alkalines such as potash but I love the luster from potassium as well as its ability to promote nice color. The down side is it makes a fatter glass. Potassium nitrate is a great balance.

If this was easy ( it's not) when you get what you want, no one will be able to copy you. That's been an advantage for me now for over thirty years. I'm not a very good glassblower.
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Old 10-25-2019, 06:52 PM
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Quote:
Originally Posted by Josh Bernbaum View Post
In fact I just checked on your spreadsheet and the silicon % of my mix is 64.94%. I don't know what I did wrong with my division and what I thought was more like a 55.4% sand content. Maybe I'm just calculating weight percentage and not thinking hard enough about oxide percentages which the spreadsheet seems to be accounting for?
*****
you have to look at the oxides supplied, not the compounds used. Sodium carb, NaCO3 supplies NaO. Now do the atomic weights for the carbon and oxygen lost. . It's seriously different. SP I think supplies around 81 lbs of actual oxides per 100 lbs batch.
Go back to GlassnotesIV. Henry has a list of materials to oxides supplied. My spreadsheet does it as well but you took a bad side road here.
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Old 10-25-2019, 07:05 PM
Josh Bernbaum Josh Bernbaum is offline
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Everything else being equal (which is the case as best I can determine), how unusual is it that I'd have a base mix which fit SP clear four times in a row and then all of a sudden it didn't? I pay a lot of attention, in fact I obsess over details and minutiae most of the time (which is a affliction), and I am having trouble finding many if any differences between the first four that fit the clear and the last two which did not.
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Old 10-26-2019, 08:16 AM
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Sometimes someone has to stand outside and look at the aassertions. One of the things about phosphates and fluorines, or most anything that promotes either phase changes or crystals is how easily they can change in the pot. I can't speak to your details but it's hard to beleive that it worked four times and suddenly didn't. Something changed. You need to figure out what that was.
Rtae of charge, temp of charge, new materials, scales, simple error, humidity. moon was in feces...

When you moved the phosphate to the outside, I assume that was gathered. How thick was that casing. I get criticized periodically for using too thick a layer in the ring test. It's John's frequent response as to why he prefers the hagy seal. I still conduct all tests, dilatometer, ring Hagy and pull. You might consider doing a small increase in the silica, put the phosphate back on the inside, see what occurs as long as you can't do a hagy seal. If you like make the hagy seal, anneal it and send it over to me.
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