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  #51  
Old 09-02-2017, 12:51 AM
Dan Vanantwerp Dan Vanantwerp is online now
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Hi George, The positive pressure idea sort of gets to Pete's mention of a reverse blower port to remove the fumes periodically. A continuous system as you describe would seem the better solution. Problem with air turnover is the loss of heat...we might lower the fluorine attack but still decrease the element life by making them work harder.

Although, hot air could be recuperated from a clean source...
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  #52  
Old 09-02-2017, 07:15 AM
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As I noted, Carlson did well with the hole in the furnace simply blowing the fumes out of the furnace through a dedicated hole. The difficulty would be that an electric unit needs to be really tight to retain heat, so there's the conflict.
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Old 09-02-2017, 09:48 AM
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Still, if you use Richard's idea of a barrier of rammable or similar between the pot and the brick, the elements can be kept reasonably isolated from fumes. A vent in the lid can do the rest.
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Old 09-02-2017, 09:55 AM
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Coming back to one of the original seeds in this thread...how will Pete's unoxidized color base work with phosphate opals.

Are there things that could simply be added to achieve the melt characteristics that Dave has developed? Pete recommends a 2325F cook and it sounds like Dave has gotten this down a bit as he uses a wire melter.

I'm trying to get some opals cooking without starting a complete scratch, batch operation.
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Old 09-02-2017, 10:42 AM
Mitcheal Veenstra Mitcheal Veenstra is offline
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my next summer studio construction project will be building a small 2 pot gas color furnace for small scale color melting. Likely a variation of the little unit that Corning let us use in class.

I was amazed in some ways at how quickly/easily we made the colors we did in class. There are a lot of stumbling blocks along the path, and I'm sure there will be many times things don't come out the way I want them to. But the mystery and fear(?) of attempting my own color has been stripped away.

I've a set of tools to explore a new world. It's pretty darn nifty.
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  #56  
Old 09-02-2017, 10:50 AM
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You're not quite getting it. The phosphate glass is an entirely different formula with similar viscosity and expansion characteristics. As a glass, it will fit both my clear formula and the clear base formula that has a good affinity for color as well.

I have melted Dave's phosphate and it's a very nice glass. It fit my basic portfolio the last time I tried it. Dave is spot on with one thing and that is to replace the calcium with Strontium. It makes what is difficult, easy. If you don't you'll see Apatite crystals everywhere. The only way to avoid hat in a calcum based phosphate is to melt at 2400F or hotter. Even so, I think it could have trouble being melted cold and I did melt it at about 2275F as I recall.

Now you will get an opal glass melting my color formula using silver but it will be a variation on many amber tones, never white. It strikes in many ways similarly to a phosphate which draws from the pot clear and then cooled substantially. Then on reheating the phase separation occurs more in the form of colloidal strands which are big molecules tending to reflect light rather than to allow light to be transmitted. They grow, they collapse, they grow again, always getting a bit fainter and that's pretty much true of any of the crystal/colloidal growth structures in glass.
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  #57  
Old 09-05-2017, 07:00 PM
Dan Vanantwerp Dan Vanantwerp is online now
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I definitely wasn't getting it. I went back to the archives and Glass Notes to try and get a better handle on the various glass formulations and nomenclature.

Someone as unfamiliar as myself with color chemistry may not recognize that a phosphate "base" glass will be white (on striking). This was confusing me. Dave's glass is white, low-temp melting and low-devitrifying, a major accomplishment. The color threads on opal phosphates now make sense in that most of them would use a constant amount of sodium tripolyphosphate (STPP) in place of bone ash, and add colorants on top of the white. The Penland additive formulas would be used this way for the opal colors.

I'd like to get Pete's potassium clear glass batch for my normal clear, as well as my chalcedony colors, and Dave's phosphate batch to make other opal colors. This seems like the best way for me to open up a world of colors in my little two, 17 lb pot world. As I've mentioned, I don't have the facilities to store all these ingredients.

My intention now is to call East Bay and ask for a custom mix of Dave's most recent formula as follows:

"Here's what I've been melting in pounds:

Sand - 97.5
Soda Ash - 36
Hydrated Lime - 5.5
Strontium Carb. - 9
Zinc Oxide - 3
Borax 5 mol - 9
Alumina Hydrate - 4.5
Lithium Carb. - 1
Potassium Nitrate - 1
Sodium Tripolyphosphate - 6.5"

Want to be sure Dave is fine with this. I could add back the STPP separately as the Penland formula for Opal Red has a slightly lower bone ash contribution. I'm excited to get into this but know there will be many questions and don't want to step on any toes in the process.

Thanks!
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  #58  
Old 09-06-2017, 07:05 AM
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Jim may not have the STP and don't confuse it with TSP. Hydrated lime is not a generally popular form of calcium either. It may well be the case that you are not going to buy enough of the stuff to make it worthwhile for anyone to mix. Mine always came as a 1000 lb minimum. I did not recall that stuff having that much alumina in it and I'll go back and check.

In my shop, I have five base formulas that do different things but still play well together. I think John C has something like eleven now.
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  #59  
Old 09-06-2017, 09:47 AM
Dan Vanantwerp Dan Vanantwerp is online now
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Waiting for Dave before anything. Then, I'll find out the minimum and perhaps some others have had an interest in achieving the colors Dave has described. Sounds like the STP is pretty easy to come by and may require some variable amounts based on the colors anyway.

My friend had a custom batch made up by East Bay and he sent Jim one of the ingredients. The results were not great and he figures it may not have been mixed (well) prior to bagging...similar to the SP color base.

That brings up an interesting question in batch production: is SP color base made up bag by bag? If a large amount like 1000lbs is produced and the final 50-100 lb bags are not mixed well...how does it ever get mixed? 1000 lbs of powders, flakes, crystals, etc layered into a hopper and bagged would never mix right if not mixed well prior to bagging. These must be layered in the bags and if they require mixing they were made individually.

In that case, it doesn't seem like the company should care that much if the order size is 2 bags or 50 bags. Just provide a sliding pricing scale based on volume and make it easy for small and large glass consumers to buy batch.
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Old 09-06-2017, 05:38 PM
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My issue with SP on custom mixing has remained the same: Cleaning the mixer. At one point when I was doing color work for Josh Simpson's corona platters, he wanted SP to mix it and I said I doubted it would work. I had done the mixing at that time. It didn't work. There were some ruffled feathers and when questioned about cleaning the mixer, Tom said "You have to ask to have the mixer cleaned."
I'll leave that without comment.

The smaller your mix, the greater likelihood for error. Maybe Dave would mix and sell it to you.

SP color base isn't really mixed at all as I understand it. The proportioned chemicals are put in bags. You have to do the mixing.
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  #61  
Old 09-06-2017, 06:51 PM
Dan Vanantwerp Dan Vanantwerp is online now
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It's pretty fascinating to hear about things like that. Good thing they are not in the food industry.

Maybe there is a future for expansion in the batch industry for someone who wants to work with the smaller glass shops. Meticulous detail and some follow up quality control sounds like a much better business model than trying to make cullet. Especially if you target the electric furnace owner and come up with something more element friendly.

I'd like to support those directly responsible for these glasses if Dave (and/or you) are interested. I'm guessing, though, that when you put the effort into making a batch you want to get the direct benefits of your hard work.

It hasn't gone unnoticed by me that you are very particular in determining the amount of screening that an ingredient needs before use. Those little "devil in the detail" things just don't show up in a recipe and can mean all the difference in success or failure. I'm also aware that going to a batch company may be hit or miss in terms of those details.

Ah well...so the adventure begins...
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  #62  
Old 09-06-2017, 08:32 PM
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Those are really rather large mixers, holding 1000 lbs or more. If something sticks behind a fin in a big batch, it's probably not that significant. A small batch is. I do ask for a clean mixer using those services and I don't use them often.
I use a small mixer these days from Home depot. For the class, we had two. They hold up to about 100lbs. It's quite serviceable for a small shop and very easy to clean and I'm rather fussy about it if I am making color mixes. If I'm running a cadmium mix I prefer to have a clear mix in between it and any other color. Sometimes I clean it with cullet and throw the cullet away. There's lots of ways to do that. I do think expecting a company used to dealing in tonnage to be even capable of doing the equivalent of craft beer isn't really a reasonable expectation.
I think dave does it in five gallon buckets actually.
And yes grain size really matters. I always use very fine screens on feldspars which I would not have thought would matter. Manganese dioxide is another one. Moisture makes some materials clump more easily than others despite how fine grain they are. I don't like clumps. Sometime try making pancakes using a joy of cooking recipe and when you get to the part where they want you to sift the flour, try it with and without sifting. Guess which one makes the better pancake?

As the German saying goes "Well mixed is half melted"
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  #63  
Old 09-06-2017, 10:17 PM
Dan Vanantwerp Dan Vanantwerp is online now
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That German saying is pretty darn perfect...

I recall from Dave's notes as he worked through the phosphate issues that he started wetting the batch and found it helped.

Dave, I'd like to know if your latest formulation with low modifiers still likes to be wetted. AND...what is your process for doing so?

Seems like a little water in a batch would make it like a paste...or a pancake batter???
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  #64  
Old 09-07-2017, 06:10 AM
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You might not hear from Dave for a while. He has a hurricane to worry about.
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  #65  
Old 09-07-2017, 06:48 AM
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the lime is not going to be very happy with being wet and I suspect that to be true of the alumina hydrate as well. They both already have bound chemical water. Between the soda Ash and the lime, if you get it too wet, it comes unmixed. I would try it dry before I did anything like that. I don't wet my batches at all.
The lime wet will eat your skin, fast
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Old 09-07-2017, 09:21 AM
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OK, first off, no manufactured batch is going to work for phosphates because the calcium content is too high. It's the calcium that turns it into chunky style sandpaper.

Second, It's just not that tough to mix small runs of batch for color. An inexpensive digital scale, a 5 gallon pail and a paint mixer on a drill work great for mixing 10-15 pounds of batch. Check your moisture contents of your materials and either compensate on your calculations or bake it out in the oven in baking dishes. Doing small batches makes the bake it out option a good one. More foolproof. You do need to be exacting on measurements due to the small batch size.

From there you'll have to do a few throwaway runs in your melter to find out what expansion is going to be required for your melter. If you insist on using the throwaways you can add alkalais (1st column of periodic table) if you're low, just keep them off the pot walls until they melt in. If you're high you can try adding zinc or boric acid. You're limited on zinc because it goes opaque around 5-6% and boric acid sometimes makes bad cords.

You'll want to track all of this on a spreadsheet. If you don't have one email me and I'll send you mine.

Water on the batch not an absolute requirement, it just helps keep the dust down. A garden pump sprayer to spray it on the batch at the end of mixing, after it's for sure thoroughly mixed, is my weapon of choice.

Gotta run for the moment. Hit me with more questions and I'll try to dig out a list of the past posts here that might help. As Eben points out, we're in full on hurricane prep and I'll get to all that when I can.
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Old 09-07-2017, 10:25 AM
Dan Vanantwerp Dan Vanantwerp is online now
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I'll ask some questions in line to your post...

Gotta run for the moment. Hit me with more questions and I'll try to dig out a list of the past posts here that might help. As Eben points out, we're in full on hurricane prep and I'll get to all that when I can.
Sorry that I forgot you are from Florida...stay safe!

OK, first off, no manufactured batch is going to work for phosphates because the calcium content is too high. It's the calcium that turns it into chunky style sandpaper.
I was hoping to send your latest formula to a batch maker and have them do a custom run (perhaps sans the STP). I just don't have much space to store bulk chemicals. Montana would actually be a good environment as we are very dry here. This is definitely plan B for me. I was looking for permission or to request an intellectual right percentage be established for you with East Bay. Jim mentioned this would be done for Pete's base clear. Sounds like there may still need to be some tweaking though based on the furnace...not a one off formula (addressed below).

Second, It's just not that tough to mix small runs of batch for color. An inexpensive digital scale, a 5 gallon pail and a paint mixer on a drill work great for mixing 10-15 pounds of batch. Check your moisture contents of your materials and either compensate on your calculations or bake it out in the oven in baking dishes. Doing small batches makes the bake it out option a good one. More foolproof. You do need to be exacting on measurements due to the small batch size.
Agreed, I could do this if I had the space for all the ingredients. May go down this route in the future...Thanks for the tips.

From there you'll have to do a few throwaway runs in your melter to find out what expansion is going to be required for your melter. If you insist on using the throwaways you can add alkalais (1st column of periodic table) if you're low, just keep them off the pot walls until they melt in. If you're high you can try adding zinc or boric acid. You're limited on zinc because it goes opaque around 5-6% and boric acid sometimes makes bad cords.
This is the part the that surprises me...I've got a melter that easily goes to 2100...why would my melter need a slightly different mix than your melter to achieve a ~96 COE? Is this that..."doesn't cross the street" thing I keep reading about? What are good ballpark percentages to add (10 lb batch, a little low, add X% Na, K, Li)?


You'll want to track all of this on a spreadsheet. If you don't have one email me and I'll send you mine.
Will do...

Water on the batch not an absolute requirement, it just helps keep the dust down. A garden pump sprayer to spray it on the batch at the end of mixing, after it's for sure thoroughly mixed, is my weapon of choice.
Another great tip but I'd try without first as Pete suggests.
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Old 09-07-2017, 12:17 PM
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I don't view 2100F as very hot and things are going to have to be coaxed into existence with very small charges. If it was me, knowing what I know, I would in fact start with a bag of SP color base, mix it and do some simple melts. See what problems you encounter at that level. I think they could UPS you a bag of the color base. Its only difference is it contain no nitrates or antimony so it doesn't fine out well. Mess with it. A simple search here will yield up varying silver and copper ruby formulas. I did not care for those colors in the Sp87 I used for a class back in 2013 but I didn't like the feldspar and that has changed to minspar now after the Kona plant burned to the ground.

But get your sea legs first, It's not hard but it's not easy either. Process adherence is your friend. The phosphate, which if Dave or I say is easy, isn't really. You need to have a sense of when it is and isn't working. You tend to know right away. By using SP87 color base, you should have no compatibility issues initially. You'll get them once you become overconfident.
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Old 09-07-2017, 12:38 PM
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Break time so some quick answers..

---------------------
I was hoping to send your latest formula to a batch maker and have them do a custom run (perhaps sans the STP). I just don't have much space to store bulk chemicals. Montana would actually be a good environment as we are very dry here. This is definitely plan B for me. I was looking for permission or to request an intellectual right percentage be established for you with East Bay. Jim mentioned this would be done for Pete's base clear. Sounds like there may still need to be some tweaking though based on the furnace...not a one off formula (addressed below).
-----------------------------------------

That's fine, I don't care much about rights etc. he would be welcome to just go ahead and use it but I would simplify it first (fewer ingredients) from what it is.

You must have the sodium tri poly phosphate or you have no phosphate. Everything else I tried for phosphate was difficult to get to melt well. It's a very common chemical, you can buy it on Ebay or from any chemical supply source or some janitorial outfits.

Always check the moisture, it can increase or decrease from the last check wherever you are. Wet chemicals are shipped to Montana....you can guess the rest.

You're going to have a whole lot less trouble if you eliminate most variables up front. Easier diagnosis if thing do go wrong too.


------------------------------------------
Agreed, I could do this if I had the space for all the ingredients. May go down this route in the future...Thanks for the tips.
--------------------------------------------
It takes very little space if you really want it to. You can buy materials in small quantities from pottery supply outfits and a few other folks.

------------------------------------------------

From there you'll have to do a few throwaway runs in your melter to find out what expansion is going to be required for your melter. If you insist on using the throwaways you can add alkalais (1st column of periodic table) if you're low, just keep them off the pot walls until they melt in. If you're high you can try adding zinc or boric acid. You're limited on zinc because it goes opaque around 5-6% and boric acid sometimes makes bad cords.
- This is the part the that surprises me...I've got a melter that easily goes to 2100...why would my melter need a slightly different mix than your melter to achieve a ~96 COE? Is this that..."doesn't cross the street" thing I keep reading about? What are good ballpark percentages to add (10 lb batch, a little low, add X% Na, K, Li)?
-----------------------------------------------------------------
Yup, this is one of a number of things that will not cross the street. I used three different melters, all requiring a different E&T number, 91, 93 and 95. This is one thing that got me mixing small amounts of batch, to satisfy the particular melter I would use. This assumes you want craftsmanship in the sense of being spot on with expansion so no worries about problems later. No pre-mixed batch is exactly right for all melters, or all colors. I feel I'm OK within a couple milimeters of bend in a thread test but also like to check with a polariscope if I'm doing something new or problems arise.


The spreadsheet is what you use to figure how to bail yourself out and to correct the next melt. This is it's single most valuable function. Knowing where you've been and how to get to where you want to go. On my side of the street every millimeter you're off on a thread test is equal to .6 in my spreadsheet.

Now you get some reading homework:

http://www.davebross.com/GlassTech/g...atibility.html
http://www.davebross.com/GlassTech/g...litypage2.html
http://www.davebross.com/GlassTech/polariscope.html



More fun things to do with phosphate....

Put a few tenths of a percent in your clear. It does very nice things for the appearance. Thank Mr. Scholes for that one.
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Old 09-07-2017, 01:45 PM
James Burts James Burts is offline
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Mitcheal--

What class was it that you took? I haven't noticed anything run at Corning that was mixing colors, but would be interested in finding it if it was run again.

--James--


Quote:
Originally Posted by Mitcheal Veenstra View Post
my next summer studio construction project will be building a small 2 pot gas color furnace for small scale color melting. Likely a variation of the little unit that Corning let us use in class.

I was amazed in some ways at how quickly/easily we made the colors we did in class. There are a lot of stumbling blocks along the path, and I'm sure there will be many times things don't come out the way I want them to. But the mystery and fear(?) of attempting my own color has been stripped away.

I've a set of tools to explore a new world. It's pretty darn nifty.
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Old 09-07-2017, 02:31 PM
Josh Bernbaum Josh Bernbaum is offline
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Quote:
Originally Posted by James Burts View Post
Mitcheal--

What class was it that you took? I haven't noticed anything run at Corning that was mixing colors, but would be interested in finding it if it was run again.

--James--
Chuck Savoie was teaching there this summer. Maybe that's it. Would have liked to go to that one but wasn't able to.
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Old 09-07-2017, 02:37 PM
Dan Vanantwerp Dan Vanantwerp is online now
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I was going to ask more questions but am pulling back to focus on this...

Yup, this is one of a number of things that will not cross the street. I used three different melters, all requiring a different E&T number, 91, 93 and 95.

E&T is calculated so I'm guessing this all has to do with how "melty" the glass is. Seems "melty" has become a word...I hear it all the time in cheese burger commercials.

Is the only difference in your melters the heat they can achieve?

Does a lower E&T require more or less heat? I'm going to PM my email for the worksheet right after posting.

What is the E&T for SP87? If it's 87 I'll have to laugh at myself.

and this...
he would be welcome to just go ahead and use it but I would simplify it first (fewer ingredients) from what it is.
You know what I'm going to ask here...
Also, my intention in leaving out the STP was simply for flexibility down the road. One of the Penland formulas used slightly less (bone ash) for opal red than for all the other opal colors. I know how to add more but removing chemicals from batch sounds tricky


As to Pete's point...
My furnace can certainly go beyond 2100...I've been cooking the chalcedony at 2180 easily and imagine 2300F would be doable, but not healthy for it.
I'll get some color base and try some things. These low temp, low-toxicity opals are what really interest me though. I see your point about getting some experience under my belt first. It helps to hear that it is not as easy as it sounds.

By the way...thanks to folks for putting up their melt schedules.
I recently found that a 2180 cook (8hrs), 1900 squeeze (4hrs) and 2112 work temp got rid of a lot of seeds! This is Crystalica cullet.
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Old 09-07-2017, 03:39 PM
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Daves phosphate melts well but I don't think he said easily
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Old 09-07-2017, 03:40 PM
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Quote:
Originally Posted by Josh Bernbaum View Post
Chuck Savoie was teaching there this summer. Maybe that's it. Would have liked to go to that one but wasn't able to.
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Chuck and I were partners in the color rod deal. He knows his stuff.
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Old 09-07-2017, 04:33 PM
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Quote:
Originally Posted by Dan Vanantwerp View Post
These low temp, low-toxicity opals are what really interest me though.
You can't get much more low temp than a fluorine, although I suppose toxicity may be a diff story. But I got hardly any odor off the melts by keeping temps as low as possible for gathering. Last time I did fluorines (in a gas unit of course), I was gathering at 1875F, it's such low viscosity stuff. I know you're more into phosphates but just wanted to add that to discussion for comparison.
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