CraftWEB Hot Glass Talk  

Go Back   CraftWEB Hot Glass Talk > Hot Glass > General Hot Glass Discussion

Reply
 
Thread Tools Display Modes
  #1  
Old 07-26-2020, 10:51 AM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Small stones in glass from homemade batch

I've been mixing my own phosphate glasses the past several weeks, and they've been doing fairly well with the exception of my last two melts in which I'm seeing small stones throughout the melt. (like 1-2 per gather at worst) This latest melt was a bit better than the previous, but still some small stones, and on this latest melt most of the stones were toward the top half of the melt. The 14" pot, one of Pete's tabular alumina ones, is only 8 melt cycles old now, and my crown looked good still before I turned on this furnace. Mostly same bags of materials I've drawn from for the first 6 melts (which had few to no stones in the glass) that I'm still pulling from for these last two in which I've seen the stones, with the exception of new bags for sand and and soda which I use the most of. I am toward the bottom of many of those bags, and not sure if "un-meltable" things can sink down to the bottom of a bag.. But my only thoughts so far are that, even though the first 6 melts did pretty ok with the same temps/times, that I need to melt longer maybe? I'm already at 2350F for the temp and hoping to not have to go hotter. And next thought, and perhaps an even more important step is to have to sift most (or all) of these ingredients now? I've only been sifting the sodium and potassium carbonates to get the lumps out, but I'd like to get some feedback on what else of these other ingredients I'm going to list should be sifted:

Sand (200 mesh)
soda and potash (already sift/20 mesh sieve)
whiting
alumina hydrate
borax pentahydrate
strontium carb.
zinc oxide
lithium carb.
antimony trioxide
STPP
sodium nitrate (which goes thru coffee grinder)

I have a 20 mesh sieve and a 100 mesh (which I've used in the past for feldspar but seems like it took forever to get particles through). I'm suspecting that of the above list, the STPP and alumina might be the most important to sift? Everything else is just so damn powdery (including alumina), but maybe there are some larger chunks I haven't been noticing? Any thoughts on next steps to try to get rid of these stones? It really does seem to be nice, clean, good-working property glass otherwise. And it's still magic to me to see all these powders mix together to make a custom glass body, but man it's frustrating when something worked for a while and now it doesn't for some reason. Kudos to Tom and Spruce Pine for being so consistent with their batch all these years. Others too I'm sure, I'm just most familiar with the consistency from SP.
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #2  
Old 07-26-2020, 10:56 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,184
Pete VanderLaan is on a distinguished road
dump more whiting and increase the strontium
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #3  
Old 07-26-2020, 04:31 PM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Well I had increased the strontium and dropped the whiting (a tiny bit) on this last melt vs. the previous melts. But even before that change, I'd been noticing very few to no stones so I'm not sure that explains the problem I'm now seeing.
My former CaO2 was 2.71% and current CaO2 is 2.53%. My former SrO was 4.69% and current is 5.29%. I also increased lithium from previous melts to see if that'd help get everything into solution with no 'stragglers'. LiO2 was 0.27% and currently is 0.45%. I think I'll take that back down though, because this melt was a bit longer of a working glass than (even I) like. It stayed hot for a while, but maybe that's an effect of the increased strontia as well?
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #4  
Old 07-26-2020, 05:02 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,184
Pete VanderLaan is on a distinguished road
My opinion is that the stones are coming from the calcium joining up with the phosphate. Lithium is a risky way to loosen up a glass since it affects your pot as well. Calcium and Strontium are just about interchangeable as far as the expansion factors go.

I was under the impression that you started seeing this when you had Neodymium in high percentage in the glass and then were mucking around with selenium. So, this is the base now with the same problem?
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #5  
Old 07-26-2020, 08:59 PM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Quote:
Originally Posted by Pete VanderLaan View Post

I was under the impression that you started seeing this when you had Neodymium in high percentage in the glass and then were mucking around with selenium. So, this is the base now with the same problem?
Yup, I did start seeing the stones on my previous melt that had the Nd/Se on the phosphate base. On this current melt from this past week, I went without any colorants but did modify the base, mostly because I've wanted to see how low I can get away with on the P2O5 content but still have it strike. In dropping the STPP amount on the spreadsheet, I had to do some other adjustments for expansion so that's when I decided to mess around with changing the lithium, calcium, and strontium a bit while I was at it. There were less small stones in this latest melt, and mostly towards the top of the pot strangely enough, but small stones were still there. A 1.08% P2O5 didn't strike at all for me as it turns out (previous were 2.12%), but I did make a pretty surprisingly clear glass even without erbium.

I get what you're saying Pete about the calcium and phosphorous not getting along but it's still mysterious to me that I hadn't been seeing the stones (or very few anyway) on the 6 melts prior to that Nd/Se try, and all of those were the same base as the Nd/Se melt, just with different colorants (or plain white). If I remember correctly, I think my calcium content is right around what Dave used in his Brossphate base, and he's been one of the proponents of less calcium with the phosphates. I'll try to reduce the whiting even more, but I guess I'm still hoping that sifting will help with this stone problem some.
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #6  
Old 07-26-2020, 10:48 PM
Hugh Jenkins Hugh Jenkins is offline
Registered User
 
Join Date: Sep 2006
Location: Honoka'a, HI
Posts: 1,007
Hugh Jenkins is on a distinguished road
I had at one time concluded that STPP was not an easy component to melt. It did need to be sifted in with other agents to make sure it did not concentrate in any lumps. The reason it creates an opal is because of its relative insolubility. I also believe that melting it with Antimony oxide can be a problem because the antimony is a reducing agent in the cooling phase of finishing a melt. Any moist components can cause clumping if measured in close contact with other powdery materials. Try sifting everything except the silica together to get some distribution and then putting that into the mixer. Don't let stuff sit together unmixed in a bucket for any period.
__________________
Aloha, Hugh
Reply With Quote
  #7  
Old 07-27-2020, 04:14 PM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Quote:
Originally Posted by Hugh Jenkins View Post
Don't let stuff sit together unmixed in a bucket for any period.
Thanks Hugh for your input on this. I've wondered about the above statement before. Spruce Pine make a color-base that comes unmixed, and one has to mix that before melting. I have a half ton of the stuff and haven't ever used it yet. I might never use it, but I still have it sitting around after 6 or 7 years. But that got me wondering if the powdered materials 'go bad' after being in contact with one another for years. I know moisture can be an issue, but I imagine that could be an issue whether it's one material in a bag/bucket or several together.

I also imagine that, unless the batch has been pelletized after mixing, that one wouldn't want it to sit too long after mixing. I used to mix right before tossing into the preheated furnace, but that meant having to wake up early, and I cherish my sleep these days. So lately I've been mixing the afternoon before I start a melt the following morning, and therefore the mixed batch sits in the mixer overnight. I've been thinking this isn't too long for it to sit, but I don't know for sure. I suppose I could always start up the mixer again for 5-10 min right before it goes in the furnace if I had to. One other nice thing about mixing the day before is that the dust in the mixer has time to settle.

Also, I just mixed up a new batch this afternoon and I sifted everything except the sand through a 20 mesh sieve. Well, almost everything– the strontium carb. was painfully slow to get to go through even the 20 mesh, so I gave up on that one and didn't sift. I did find quite a bit of larger particles at the bottom of the sieve for the aluminum hydrate in particular. Wondering if that had been contributing to stones. And dropped calcium and brought up strontium a bit more as Pete had suggested. And cut some of the lithium too to closer to where I started with my original mixes from weeks ago. Maybe that's too many changes at once, but I'm shutting down after this melt, so won't have another chance to tinker with it until the fall.
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #8  
Old 07-27-2020, 05:48 PM
Hugh Jenkins Hugh Jenkins is offline
Registered User
 
Join Date: Sep 2006
Location: Honoka'a, HI
Posts: 1,007
Hugh Jenkins is on a distinguished road
If batch actually gets wet, there can be migration of the soluble fluxes and that can spoil the batch. I have stored batch for years and if kept dry had no problem, but in unlined cardboard drums you can start to see wet diffusion into the container.
Spruce Pine color base was without both the nitrate and the antimony components so that reduction or neutral melts could be made. You could add those on your own if needed. But once again if moisture got into the stuff it was very hard to remix completely.
Alumina is most easily melted as a feldspar, but the ceramic sources for that often carry some iron as well. Your large alumina articles might be the problem you are looking for. That is an inconsistent component in your mix That also might physically migrate in storage.

Referring to the history discussion in another thread, Kurinsky claims that almost all ancient glass was fritted and then remelted to make cullet that was remelted again for most production. All those remelts may have been needed to completely mix components. They were fighting against somewhat lower melting temperatures for the raw batch melting phase.
__________________
Aloha, Hugh
Reply With Quote
  #9  
Old 07-27-2020, 05:50 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,184
Pete VanderLaan is on a distinguished road
Calcium and phosphorous have a special relationship. I suspect you're making apatite crystals. I'd consider using the Bross formulation to start, not SP87.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #10  
Old 07-27-2020, 07:27 PM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Quote:
Originally Posted by Pete VanderLaan View Post
I'd consider using the Bross formulation to start, not SP87.
That's for others to read, right? You know I'm mixing from scratch, I just brought up the SP color base because I've had it lying around forever and thought I'd ask about storage. I did use Dave's Brossphate as a starting off point on these melts, but I've modified it and then modified it some more in some ways, and in other ways I haven't. All of them that I've mixed from scratch have had much better results than when I first started trying phosphates by trying to mix some STPP into spruce pine's oxidized batch early last year.
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #11  
Old 07-27-2020, 07:51 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,184
Pete VanderLaan is on a distinguished road
well, OK. You're the one with the stones. I'm simply saying that Apatite stones are what the two elements create. No more. If it was me, I'd get more of the calcium out and increase the strontium. I don't think the Antimony has a thing to do with it.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #12  
Old 07-27-2020, 10:06 PM
Ed Pennebaker's Avatar
Ed Pennebaker Ed Pennebaker is offline
Registered User
 
Join Date: Apr 2002
Location: Red Fern Glass near Green Forest, AR
Posts: 205
Ed Pennebaker is on a distinguished road
The Spruce Pine color mix can be problematic when it gets old. I had some old bags that had some large chunks of what I'm guessing was the soda ash that had solidified. I tried a large wood rasp on the chunks and could return them to powder but it wasn't fun. The next batch I used Steinerts frit maker in a large bucket to get the chunks as small as possible. Then I could break the small chunks into powder by crushing them with the rasp. I screened the entire batch both before and after tumbling in the mixer, melts came out fine.
Reply With Quote
  #13  
Old 07-28-2020, 07:24 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,184
Pete VanderLaan is on a distinguished road
SP Color batch is problematic from the start in that the proportioned chemicals are simply put in the bag but they're never mixed. When fresh, they should be reasonably free of clumps but a number of the materials won't stay that way, so, if you try to use it, it's going to be an uphill battle.

When I get materials like Potassium carbonate into the shop, I open the bags and put the stuff in big ziploc bags. You can buy two and three gallon ones on Amazon.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #14  
Old 07-30-2020, 11:32 PM
Sky Campbell's Avatar
Sky Campbell Sky Campbell is offline
Registered User
 
Join Date: May 2002
Location: Gainesville FL
Posts: 1,022
Sky Campbell is on a distinguished road
Has anyone tried vacuum sealing? Those bags do come in rolls and it may be a way to beat the clumping. For me half my stash has been beaten by the tropical climate. . I wonder if they would last longer before deteriorating?
Reply With Quote
  #15  
Old 07-31-2020, 08:45 AM
Eben Horton Eben Horton is online now
Registered User
 
Join Date: Apr 2002
Location: Wakefield, RI
Posts: 4,779
Eben Horton is on a distinguished road
Quote:
Originally Posted by Sky Campbell View Post
Has anyone tried vacuum sealing? Those bags do come in rolls and it may be a way to beat the clumping. For me half my stash has been beaten by the tropical climate. . I wonder if they would last longer before deteriorating?
I have not but when ever I have extra castable bags that are open or closed, I take that plastic cling wrap that is used for cocooning boxes on a pallet and wrap the bags up tight. It’s air tight and I have had castsble last a looooong time this way.
__________________
<eben epoiese>
Reply With Quote
  #16  
Old 08-02-2020, 11:22 AM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Happy to report that this last melt was stone-free and nice looking glass.
I sifted everything except for the sand and the strontium (strontium just took forever to go through the sieve), and did find some larger particles of alumina hydrate at the bottom of the sieve. I also reduced my calcium content even more (but still a bit in there) and increased strontium. Now to work on fit with my clear (again). I had my earlier phosphate melts from a few weeks ago fitting just fine and consistently (five in a row) at the same expansion number, at about a 96.3 on a spreadsheet calc. But with this current melt, where I changed around some proportions of constituents, fit is off again, even with that same spreadsheet-calculated expansion. (exp. seems to be a bit high, I'd guess maybe even by 2 points or so based off my ring test results) So, could a change in viscosity due to my proportion adjustments be showing it's head here and altering compatibility in this case?
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #17  
Old 08-02-2020, 12:37 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,184
Pete VanderLaan is on a distinguished road
Quote:
Originally Posted by Josh Bernbaum View Post
Happy to report that this last melt was stone-free and nice looking glass.
So, could a change in viscosity due to my proportion adjustments be showing it's head here and altering compatibility in this case?
It could indeed. The glass needs the littlest bit of calcium to strike anyways. If I was approaching that, I would use silica to adjust the glass down. It's deceptively powerful as that tool and having a little more silica in your glass doesn't usually hurt a thing.

The old German saying comes in here:

"Well mixed is half melted. "

Now don't charge too fast.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #18  
Old 08-07-2020, 08:38 AM
Eben Horton Eben Horton is online now
Registered User
 
Join Date: Apr 2002
Location: Wakefield, RI
Posts: 4,779
Eben Horton is on a distinguished road
To celebrate, I hope you can play track 12 on Hendrix’s Are you experienced album.

__________________
<eben epoiese>
Reply With Quote
  #19  
Old 08-07-2020, 09:42 AM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 716
Josh Bernbaum is on a distinguished road
Quote:
Originally Posted by Eben Horton View Post
To celebrate, I hope you can play track 12 on Hendrix’s Are you experienced album.

Haha, good one. Had to look that up.
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #20  
Old 08-07-2020, 10:54 AM
Eben Horton Eben Horton is online now
Registered User
 
Join Date: Apr 2002
Location: Wakefield, RI
Posts: 4,779
Eben Horton is on a distinguished road
Got to got to got to get away.......
__________________
<eben epoiese>
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 08:22 AM.


All published comments within these message boards are the opinions of its contributor and does not represent
the opinion(s) of the owner(s) of this website. Please see the Terms of Use file for more details.

Books to Help Artists Avoid Online Scams: Top 10 Email Scams | Social Media Scams

Powered by vBulletin® Version 3.7.2
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
© CraftWEB.com. Opportunity Network. 2008. All Rights Reserved.