CraftWEB Hot Glass Talk  

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

Reply
 
Thread Tools Display Modes
  #1  
Old 09-22-2022, 11:36 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
sintering pots

Sintering alumina is a thermal process whereby the molecular structure of alumina is altered and becomes very different when interacting with molten glass. I am intentionally keeping it to this circumstance.
Back when I was first marketing pots to Ed Skeels, he did indeed sinter them all and said it enhanced their performance. I've found this to be true. Les Grupp and I both wanted High Temp to build a furnace capable of sintering to a degree but it was never built and I don't see it happening. John Croucher would take his pots from Fastner and sinter them. It is not a process available to anyone who can't get to at least 2550F so wire melters can't do it.

Ideally one would take the pot to 2650F and many furnaces are not built of materials that will withstand that temperature range but even taking the pot to 2550F is a help in the process. Three hours at that temperature makes for a stronger pot. The pot must be brand new and never had glass in it.
Take the new pot up through quartz inversion just as you normally would. When you get to 2300F, just keep on going to at least 2550F, higher if you can. Three hours. Then bring it back to your normal charging temperature and act like you usually would.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #2  
Old 09-22-2022, 12:42 PM
Richard Huntrods's Avatar
Richard Huntrods Richard Huntrods is offline
Registered User
 
Join Date: Aug 2003
Location: Vancouver Island
Posts: 1,223
Richard Huntrods is on a distinguished road
Pete,
Can you elaborate on "stronger"? More resistant to glass damage? More resistant to thermal shock?

I can't imagine bouncing a crucible off the floor, so strong seems a word that needs further definition in this context. :-)

Thanks,
-R
Reply With Quote
  #3  
Old 09-22-2022, 01:27 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
Far less prone to dissolution.

One of the tests that works well when evaluating a crucible is to fill it halfway with a strong cobalt laced glass. Run it and run it hot.

Then remove the crucible from the furnace and saw it up. You will be able to see clearly how much the cobalt glass saturated the alumina potin the exposed interface. Sintering reduces that saturation which suggests that the pot will be more resistant to dissolution from general clear glass attack as well.

But it really is ineffective below 2550F to see any tangible improvements. It really works best at about 2700F but it's hard on your furnace unless you built for that.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #4  
Old 09-22-2022, 02:14 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
Registered User
 
Join Date: Apr 2010
Location: Sweden
Posts: 1,420
Michael Ahlefeldt-Laurvig is on a distinguished road
I had one of Pete's pot,that was shot. Used 7 months or so. Thought I would use it as a flower pot, drill a hole in the bottom . No way, diamond drill bounces around, sledge hammer bounces as high as you start. So time is a factor too.
Ive sintered green clay pots at 2800 f. 6 hours, sort of nervous , its white hot. But my furnace would take a couple hundred degrees more but its cutting it close.
Reply With Quote
  #5  
Old 09-22-2022, 03:21 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
Pots have a distinct lifespan but it's worth noting that some glasses are more corrosive or so it seems than are others. I had it suggested to me a long time ago by Frank Wooley that there were no glasses that were really more corrosive but the question was what the viscosity of the glass was at the temperature you were trying to work it. Fluorine and Lithium both dramatically lower viscosity and that allows the glass to flow more freely into interstitial spaces.

Materials like AZS have close to a zero porosity when they are in contact with glasses of any type and if kept at an almost constant temperature will do quite well. Loading the pot with glass is decidedly not keeping it at a constant temperature and what AZS does really poorly is to resist thermal shock. It breaks and in most cases with freestanding stuff is unacceptable. It does do well invested using such liners as provided by Minteq.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #6  
Old 09-22-2022, 03:22 PM
Eben Horton Eben Horton is offline
Registered User
 
Join Date: Apr 2002
Location: Wakefield, RI
Posts: 5,075
Eben Horton is on a distinguished road
You know you are there when you see stalactites forming from your crownÖÖ
__________________
<EBEN EΠOIESEN >
Reply With Quote
  #7  
Old 09-23-2022, 03:26 AM
Sean Jones Sean Jones is offline
Registered User
 
Join Date: Jan 2016
Location: Staffordshire U.K.
Posts: 35
Sean Jones is on a distinguished road
Iím building a rapid firing wood burning furnace. The intention is to get usable glass in a few hours from lighting. Itís going to be seedy but cheep on fuel and mobile so I can use it for demonstrating.
Iím making a mould for the crucibles at the moment and they obviously need to be bomb proof but quick to make as they may turnout to be single use. To that end, Iíve turned a wood pattern the shape of the pointy end of an egg and Iím about to cast a plaster box around it. I then intend to press clay into it to the box to form a thin wall pots, maybe 3/8Ē thick.
Iíd assumed, from looking here that Iím going to need to fire the pot as high as I can. Iím thinking to take them to 2300 in the wire melter and then build a custom gas kiln to re-fire them to 2600.
I canít get hold of tabular alumina so Iím using molochite grog. Not ideal I know but it works for my wire melter pots.
Reply With Quote
  #8  
Old 09-23-2022, 08:40 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
I would consider a china clay , grog and ball clay. If these are one shot deals, you're firing them green essentially and just might as well go to melt temps from there directly. Don't bother with sintering. They won't last long enough to benefit from it.
You have variables i don't know much about.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #9  
Old 09-23-2022, 01:15 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
Registered User
 
Join Date: Apr 2010
Location: Sweden
Posts: 1,420
Michael Ahlefeldt-Laurvig is on a distinguished road
3/8 thick? What braught you to that number, just curious
Reply With Quote
  #10  
Old 09-23-2022, 01:24 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
Registered User
 
Join Date: Apr 2010
Location: Sweden
Posts: 1,420
Michael Ahlefeldt-Laurvig is on a distinguished road
You do know glass is quite heavy?
This is not going to cut the cake
Reply With Quote
  #11  
Old 09-23-2022, 01:28 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
Quote:
Originally Posted by Michael Ahlefeldt-Laurvig View Post
3/8 thick? What braught you to that number, just curious
***
Cheap to make, quick to dry, expected short life. Those porcelain coffee cups come to mind. A three day color pot in the gloryhole. Buy it at a flea market for .50 cents.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #12  
Old 09-23-2022, 02:19 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
Registered User
 
Join Date: Apr 2010
Location: Sweden
Posts: 1,420
Michael Ahlefeldt-Laurvig is on a distinguished road
Ok were talking coffee cups?
Reply With Quote
  #13  
Old 09-23-2022, 02:27 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
Registered User
 
Join Date: Apr 2010
Location: Sweden
Posts: 1,420
Michael Ahlefeldt-Laurvig is on a distinguished road
When I was young and good looking, Boda glass factory was actually burning wood, I was there and saw it. So its doable. Just need a good chimney to get the draft
Reply With Quote
  #14  
Old 09-23-2022, 08:27 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
Quote:
Originally Posted by Michael Ahlefeldt-Laurvig View Post
Ok were talking coffee cups?
**
At one point in the late '70's, I made my own pots that held up to about 70 lbs. They worked well but were one shot deals based on a kyanite/ ball clay recipe. We threw them on a wheel, not unakin to throwing sand.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #15  
Old 09-24-2022, 04:17 PM
Brian Bradshaw Brian Bradshaw is offline
Registered User
 
Join Date: Jun 2016
Location: Lakewood, CA
Posts: 48
Brian Bradshaw is on a distinguished road
When I was doing my color melting back in the 80's we did the same. The pots were 20 -25lb and if you tried to throw them with bare hands you'd end up with a bloody pot. We fired them to cone 14. The glass they produced was sweet. I melted my first cad/sel red in one. They lasted a half year. I still have one left. I'm going to be using a wire melter this fall and Pete's pots. Just my 2c...
Reply With Quote
  #16  
Old 09-24-2022, 05:54 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 23,883
Pete VanderLaan is on a distinguished road
wear gloves when you throw them... Or , slipcast them.
__________________
Where are we going and why am I in this basket?
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 06:55 PM.


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 - 2022, Jelsoft Enterprises Ltd.
© CraftWEB.com. Opportunity Network. 2008. All Rights Reserved.