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Tools / Tool Envy
« Last post by Administrator on January 27, 2019, 01:28:19 PM »
Check out this babe!

Thorough mixing is a huge concern in batching. Jim Meyers at East Bay Batch told me he had a commercial food grade mixer to do the sample batches he did for me which were about 80 lbs each. Check out the price tag on something like that...even used they are thousands of $$$. I have a cement mixer I picked up for $300 and recently had issues with thorough mixing even after leaving it running for a few hours. It's pretty easy to visualize the powders just turning and hardly mixing. I'm considering adding some extra paddles and just giving it some additional hand mixing; dumping the batch into a container and loading back into the mixer.

For a test batch of 20 lbs, this product looks pretty awesome. I had issues with doing a 5 gallon bucket mix recently. I use a drill with paddle mixer and like to mix the entire bucket by turning it upside down several times. Still, without actually getting into the bucket with a scoop to mix it around I had problems with the melt.

What we need is a mix indicator. An internal control for mixing. You can't just look into a batch bucket and tell that everything has mixed when it all looks the same. I'm going to use a small amount of black tin thrown into the bottom of the bucket. A good, thorough mix will end "graying" the contents throughout. We'll see how it works. If I could just leave the pictured mixer alone for an hour or two and come back to a great batch mixture...might be worth the $300 price tag.  8)

Batch Recipes / An attempt at a SP87 like glass batch
« Last post by Administrator on January 27, 2019, 11:59:13 AM »
Corning performed an analysis of Spruce Pine that has been published in Frank Wooley's book, Glass Technology for the Studio:

Measured expansion: 94.9

SiO2 - 72
Al2O3 - 1.8
Na2O - 14.9
K2O - 0.4
Li2O - 1.0
CaO - 7.9
MgO - 0.2
BaO - 0.5
ZnO - 1.0
Sb203 - 0.2
F - 0.1

I thought it would be fun to use a batch calculator to try and dial in a formula based on this analysis. Recall, my calculator has a price/lb feature that is pretty revealing and sometimes a go, no-go answer.

I've uploaded this recipe in the calculator so you can easily play with the numbers. Here's a screenshot:

So, before we go and run out to make SP87, look at that price per pound at $0.94!  :o
Bulk buying power is the difference especially for all that lithium. This is about what I'm paying from OCR before shipping. I recently got the "snowflake" version which doesn't really require a special designation. It's simply non-pelleted, powder batch. Better than SP bricks. It did come up 12 lb bags which is kind of nice, but I don't throw whole bags in my electric furnace.

I need to add some potassium contribution from potassium nitrate as well. The SP color base formula has some discussion on Craftweb about what it has removed. I believe it was nitrates and antimony but I'll check back and comment later.

You may notice that the MgO % is pretty far off. I'd explain this by pointing to the one MgO source from typical batch...silica. Depending on your sand source you're going to have more or less MgO contribution.

The "Other expansion" is close to the measured at 93.9...about a point off. I could hone in on that number by tweaking ingredients but you might be better of making a test batch and seeing where it lies. Or just buy SP87 from the pros. ;)

I think I know. I live in an area with very few glass artists. It was different when I lived in San Diego and worked in a few studios that rented time. You ran into glass artists of all stripes and some of that rubs off on you. We have to be influenced by the people we respect. I've asked people for help or to train with them only to be ignored or just flat told no. I still have the first piece I ever made while being literally walked through the studio by a dear friend. A small paperweight that means more and more to me as time goes by. I'm not a full time glass artist and that could be a big difference in my thinking.

I trained at Palomar college which had two consecutive teachers who started as ceramic artists. The glass just took hold of them. The training was team style or, at least, gaffer w/ assistant. The teacher's approach was jarring to me as a an older student in my 30s. Sort of felt like a drill sergeant barking out orders and scolding mistakes. For me to put up with it for a couple semesters showed my desire to learn. But a lot of gaffers are this way...perhaps necessarily so. Shouting, dressing down, demanding perfection...I know a couple that split up, in part, over this dynamic being incompatible with a marriage outside the shop. Ouch! Funny thing...rather than even suggesting to the artist that their approach was too harsh, the situation convinced her that friends and family should never be gaffers' assistants.  :-\  I love to watch the teams demo at Corning. It may have taken some yelling to get the point of wordless conversation between gaffer and assistant, but I have the feeling that the better the gaffer is, the more easily they make it for the assistant to do their job. I'm at my best when I'm super chilled out while blowing...It's just glass. Is my mantra.

I've worked solo almost exclusively. I've built my own equipment and love the sense of "power" I feel in knowing exactly how something was made. Rebuilding, maintaining, upgrading becomes so much more accessible. I'd love to bring along an assistant but it would be difficult in my current situation. I live far outside the town and there just are not many glass artists around here. I see people at my glass shows and they suggest they want to learn but then you never here from them. I welcome it. I've got a lot to share so here I am.

General Discussion / Re: The Cullet Wars: Will Anyone Win? Probably not the Artist
« Last post by vitroholic on January 26, 2019, 09:59:10 PM »
I can never be sure I'm not one of those jerks sometimes, if you know what I mean...
Yes, my teacher was very good at teaching  beyond mere glassblowing, which he readily admitted wasn't his strong suit. He was mostly self taught after getting a grad degree in ceramics.
One of the things I most cherish was that during my second or third semester with the class, the teacher decided he wanted a whole new studio, so we spent the entire semester tearing out all the furnaces and building all new ones from scratch. Tank furnaces, glory holes, annealers, everything. What I learned that semester propelled me further to becoming a glassblower than the other four or five semesters I was there. It allowed me to go out on my own and make a couple of really Fu***ed up furnaces with scrounged materials (vacuum machine for a blower, anyone?) and learn how to make one I could really use.
good times!
Thanks for the post. I was surprised to get one so soon after starting the forum. Seems like there is space online for another furnace glass option. I took the time to read through the Craftweb archives post by post. Lots of techniques revealed and color tricks shared. I'm going to try and help those resurface for myself and the glass community to more easily find.

It's what we do with these things that matter. Got to keep innovating and trying new things.

Lots of jerks out there. I've met very few people willing to bring others along and foster their growth. Sounds like your instructor was such a person.  :)  I guess this forum is my way of trying to do so. That and I just love glass. Great username!

General Discussion / Re: The Cullet Wars: Will Anyone Win? Probably not the Artist
« Last post by vitroholic on January 26, 2019, 11:29:29 AM »
When I was first introduced to glass in the early 80s, my teacher had formulated the batch. It worked fine for what we were doing. He eventually got hold of the penland formula and switched to that for the optical qualities.
It was good experience to go through the batching process, going around and getting the materials, (I think the sodium nitrate came from a farm supply store) weighing everything out, mixing and shoveling it into paper sacks to throw in the furnace. I saw the teacher's thinking develop from using coarse materials to buying finer powders, and getting really nice optical qualities for the trouble.
I still think back to that original formula, though. The simplicity of a formula with less than eight ingredients. I recall it was very receptive to irridizing as well.
What I've been doing lately isn't all that optically demanding, and with all the hassle around sourcing batch or cullet, I think more about doing my own batch.
This is a roundabout way of saying thanks for posting this simple recipe that someone like me could use as a starting point.  I don't expect to take it and be in production with it tomorrow. it'll take some refining and experimentation to get it right.
  :D Your idea of starting a forum for open source information is laudable.  :D
I recall talking to a glassblower at an art fair once and asking if I could come see his studio. He said I could see the studio, but wouldn't be able to watch him work. The way he saw it, he'd spent a lot of time and money learning his techniques and he wasn't going to just give them away.
My first thought was what an ass the guy was. To begin with, I wasn't going to see some shortcut watching him and be in competition with him the next day, stealing his hard won technique. further, he stood on the shoulders of giants, like all the rest of us. His skill, which was considerable, didn't appear of his own virtue alone. I wasn't so much looking for a free class as much as some inspiration from seeing how far his work and learning had taken him.
That said, I'm not going to burn bridges by mentioning the glasshole by name.

Projects / Opal Phosphate Batch
« Last post by Administrator on January 26, 2019, 11:09:51 AM »
As I continue on this project thread, the cryolite did not show up yesterday so I made a modification to the batch in an effort to move forward.

What is Cryolite anyway?I hadn't thought of it as a batch ingredient until Pete recommended that Jordan Kube use it to help in melting his high phosphate (5%) opal batch. Cryolite is one of these naturally occurring compounds with the formula: Na3AlF6. So some sodium, aluminum and fluorine. The fluorine is what helps in the melt. Lots of the recognizable intense opaque glass colors are fluorine-based. It's an interesting element. The most highly electronegative and reactive. I've been using hydrofluoric acid in the finishing process of finishing glass. It eats glass. Even at the relatively low concentration I use it at. I'll discuss this process at some point...I think I have found THE best source for this etching material.

At higher concentrations (>4%), fluorine forms crystals in the glass that prevent light transmission. Below this level, fluorine can be used to help a glass melt. According to Weyl in Colored Glasses, it interacts with and disrupts some of the Si-O-Si bonds. This somewhat weakens the structure, lowering viscosity and in doing so helps melting. He even mentions that it has been used with great effect in making opal phosphates by preventing surface formation of apatite crystals. They form at the surface because the process requires water provided by the atmosphere. In any event, this causes the surface to become rough. My future melts will likely contain cryolite (~.5% w/w) to avoid this issue, but when the glass is encased this really becomes a non-issue.

I'll need to read more to understand the contribution of fluorines to glass expansion. Cryolite contains the following composition of oxides:
Yet, I have a calculator which estimates expansion and does not take these oxide contributions into account. When added back to the calculations, the sodium alone can create quite a discrepancy. My guess is that the fluorine makes the other components so volatile that they gas off and do not contribute to the final glass. However, this will take more reading. Fluorspar contains a similarly unattributed oxide in CaO at 59.6%. Again, very high but in combination with fluorine perhaps lost during the melt. Interesting...

I'll post on fluorine batches soon and discuss the way the calculator estimates their expansion. Pete points out that 96 LEC compatible fluorines come in around 72-75 in his estimation. We'll look at the expansion contribution a few different ways and see if a best estimator can be determined. Of course it always comes down to real world testing!  ;D
General Discussion / The Cullet Wars: Will Anyone Win? Probably not the Artist
« Last post by Administrator on January 25, 2019, 11:36:22 PM »
I recently received the email flyer from HotColorGlass that Kugler is going to offer a clear cullet. The price is a little staggering at $1.60/lb. I paid $1.00/lb for Cristalica the last time it was available. Pete has revealed that at least 2 other cullets will soon be available. This is getting really tough. Obviously, these companies all see an opportunity but are they in it for the long haul? Do they even really know? Things seem to happen when you try and melt, cool and cut (or vise versa) hot glass on an industrial scale. Who do you cast your lot with?

Batch makes sense to me but it sure has drawbacks.
- dust issues
- volume loss
- time to melt, time to charge
- the RIGHT formula question

Of course, the final point is true of cullet also. You can always mix your own and I've been playing with the idea. My first attempts just didn't stand up to the clarity of Cristalica. Perhaps barium is the answer to clarity.

Allow me to throw out some strong clear glass qualities:
- barium for clarity, modifier
- calcium for economy
- strontium to replace some calcium
- lithium for workability
- erbium for color removal
- alumina for strength/durability (hydrate, not feldspar due to concerns of contaminants)
- nitrate for melt
- potassium for clarity
- keep alkali below 18%, modifiers at above 8%, silica around 70%
- lithium between 2-5%
- antimony to fine the melt
- no borax...Pete insists this with barium is a big no-no. Glasma would disagree and so would Cristalica. So I might add some back in case the glass did not melt well.

I'll work it up in the calculator for 100 lbs and see what it gives for a 96LEC batch.

The silica is a little high but may be fine. Alkali is below 18% at 17.73%. Modifiers include calcium, barium, strontium and zinc...these add up to 8.28%. Nice potassium at 3.04%. Lithium is about .3%. Alumina at 1.5%. The calculator does not make an allowance for erbium as it is added in minute amounts...who could afford any more than that?

Other Expansion estimates a 96.3 LEC which looks pretty good compared to some other formulas I've looked at.

Will it melt? I dunno but it's no bargain! Nearly $0.68/lb before shipping!!! Plus you get to mix it yourself.
Bulk buying power allows the batch companies to make money. Most of us get the pottery store markup.

Hopefully that was a nice thought exercise for you to see how a priority set can be used to establish a first-try batch recipe.

Batch Recipes / Chalcedony
« Last post by Administrator on January 25, 2019, 10:26:46 PM »
This batch is discussed a bit in the introduction of my batch calculator:

The basis is this unoxidized glass with a bit of alumina in the form of 3 lbs feldspar.

Silica 47.42 lbs
Soda Ash 15.21
Lime Hydrate 6.78
Potassium Carb 3.94
Borax 5 mole 1.65
Feldspar (custer) 3.0

BTW: If you would rather use whiting, remember this conversion.
Lime hydrate is 74.093 g/mol formula weight. It's molecular formula is Ca(OH)2 so there is one calcium atom per molecule.
Calcium Carbonate (whiting) is 100.0869 g/mol and similarly it has a single calcium atom per molecule (CaCO3).

To make a molar equivalent calculation, I do the following:

mol/74.093g x 453.6g/1lb x 6.78lb = 41.05 mol Lime Hydrate so we just need 41.05 mol of Whiting

41.05 mol x 100.087g/mol x 1lb/453.6g = 9.17lb Whiting!

For a 10 lb Chalcedony batch add the following:
9 lbs of above
Black tin oxide: 2g*
Zinc Oxide: 30g
Iron Oxide: 2g
Silver Nitrate: 4.5g
extra soda ash: 7g

I really like to mix these smaller amount ingredients prior to adding to the batch. Make sure everything is mixed up real well which is a little easier when things are pigmented as these are.

I melt it at 2100 until pots about full. You can mix prior to cooking but I try not to. Chalcedony wants to go gray so don't do anything to push it that way! Cooking is performed with the following program:

2100 to 2180 and let soak for 10 hours.
Down to 1900 for 2 hours. (Fines the glass, removes bubbles)
Back to 2100 for work.

It may show no color upon gathering. Play with it. Let it cool, work it on the marver, heat it back up and let it go stone cold. Put heat back in and watch the colloids grow.

If you stretch it out you probably won't like it. A nice thick optic effect works well with this glass.

See Josh Simpson and Dino Rosen for the highest levels of implementation for these glasses.

*Black tin is a tricky ingredient. Pete swears you need 30g/10lbs, but this will turn black (actually dark amber) in my furnace. Try and it see what works best for you.
Batch Recipes / Clear Glasses by Dave Bross
« Last post by Administrator on January 25, 2019, 09:55:51 PM »
Dave calls this a Basic Clear with 96 COE compatability:

This is a "fancy" clear with strontium and a high potassium %. A little more $, but nicer glass.
Dave is a big proponent of the Nick Labino rule for alumina so these will be super durable.

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