PDA

View Full Version : Brossphate opal 5%


Jordan Kube
02-01-2018, 06:50 PM
So I melted this 5% opal the other day:

In pounds
Sand 7.3125
Soda Ash  2.38875
Potassium Carbonate 0
Calcium Carbonate 0.4125
Strontium Carbonate 0.675
Zinc Oxide 0.225
Alumina Hydrate 0.3375
Lithium Carbonate 0.075
Antimony 0.03975
Potassium Nitrate 0.075
Sodium Tripolyphosp. 0.93

Total 12.471

Oxides %
SiO2 66.86
Na2O 16.4
K2O 0.327
LiO 0.278
CaO 2.13
MgO 0.006
SrO 4.35
ZnO 2.06
Al2O3 2.229
P2O5 4.95
Sb2O5 0.365

Charged a few scoops at 2300 every two hours. Held at 2300 for 10 hrs and then down to 2150. It came out pretty scuzzy on top like you guys talk about some phosphates coming out. It was also pretty streaky in coloration and cordy looking. It blew out ok and the stuff I made into bar struck out beautifully after being picked up again, as always. As a note, I ground the STPP in a bullet blender in an effort to avoid some chunkies I was getting in the 2.5% melts. It also came out 4 points high after my educated guess on adjustment. Based on that and my percentages I'm thinking at least adding some silica is in order.

Any thoughts on cleaning this one up?

Pete VanderLaan
02-02-2018, 08:44 AM
I'd be inclined to simply replace that calcium with both zinc and strontium and the industrial sludge will stop. I had told you it has a tendency to be streaky and more phosphate would help there. While the silica is low, it's not that low. I assume you're allowing the stuff to get really cold before you try for the strike.

I don't particularly trust flame annealed Hagy seals.

Jordan Kube
02-02-2018, 11:21 AM
Thanks Pete, I'll give that a try.

As far as flame annealing Hagy seals, it's only so they don't crack before I get them into the annealer. They just don't look right and don't give good information if they are not properly annealed.

Pete VanderLaan
02-02-2018, 01:16 PM
Mine don't crack before they go in the box but I'm not six points off.

There are people who rely on flame annealing, an all around bad idea.

As to the phosphate. I'm not sure what that will do. It seems to me that you should be able to make the phase separation work using that alumina which is key in fluorine opals as well. I don't know if you remember when I described the streaks to you last year and you were curious. It's quite compatible and I've had that cup around for years now. The fact that it strikes on a reanneal confirms that there's plenty in there.

Bob Held first noted that up to 5% bone ash would stay compatible with your clear way back at the NCECA conference in 1968- pre GAS. But it had to melt at over 2400F. It was a true calcium monophosphate which is really hard to find now. 2300 seems a bit cold to me on that stuff you're doing. Give it another 25 degrees.

Jordan Kube
02-02-2018, 02:47 PM
Hotter was my other thought. Stuck in a wire melter for now. I ditched the borax Dave was using too.

Pete VanderLaan
02-02-2018, 04:11 PM
If you're ditching the borax then you need to use another method of keeping that melt easy. Heat helps but if the borax goes, then add more heat. Sodium nitrate would be where I would look for chemical help. . Lithium could be increased but it's pricey.
My original phosphate melts needed 2450F and very small charges. That was 1975.

Dave Bross
02-05-2018, 10:37 AM
I'm with Pete on the nitrate or lithium to replace the borax.

When I was experimenting with those I did a few melts with a lot of potassium nitrate (0.6 % up to 1%) and it upped the melt speed almost beyond belief.

I don't know what a nice compromise would be between fast clean melt at high percentages and wear and tear on the pot. I did a number of melts with the 0.6% and a few gradually upping the percentage with no sign of any worse pot damage than usual. That was using assay pots, which dissolve quickly if anything is too rough on them. I always liked that about assay pots. Canary in the coal mine if you will. I remember one batch of Phillips high COE Moretti matching batch that ate the assay pot down to paper thin in three melts.

You're using a lot of phosphorous there too. Are you gaining more in density than you might get with an extra strike/s on the lower percentage formula or are you after a one strike wonder?

Pete VanderLaan
02-05-2018, 03:27 PM
Once you're getting into this type of melt, assay pots in a high use situation is probably not the best solution.

Jordan Kube
02-05-2018, 06:08 PM
Thanks for the help guys, I'll give those things a try. I'm using a CC pot and it's holding up pretty well. Those 38 pound pots are just the perfect small pot.

Dave, yes, trying for more density, one strike wonder. When I make it into bar and pick it back up it is perfectly wonderful and homogeneous. The stuff out of the pot is gorgeous too, just a different animal. What if I melted a pot, scooped it out and then remelted it? Would the glass in the pot strike out like the bar? If no one has done this there is only one way to find out!!!

Pete VanderLaan
02-05-2018, 06:12 PM
seeking out new worlds, going where no man has gone before...

Well not actually. Lino used to frequently suggest this.

Dave Bross
02-09-2018, 03:36 PM
Yes, every time it cools and reheats it gets denser.

Kenny Pieper
02-09-2018, 04:04 PM
I never use the phosphate as just an opciifier. I think the beauty of this color is when it is still translucent. That when you get the opal effect. I like it quite weak.

Pete VanderLaan
02-09-2018, 05:01 PM
That's the light before dawn...

Marc Carmen
02-12-2018, 10:09 PM
I'm with Kenny on light translucent route. In my experience, a nice thick layer of barely striking opaline as an underlay has a much more beautiful effect than relying on blowing a commercial color thin until translucent. Perhaps this approach allows more light scattering within the color layer. Just think of how beautiful a nice chunk of cast opaline glass looks. Also, a thick layer of lighter opaline in blown work is much less temperamental in terms of striking inconsistencies and tool marks, etc. To me that is the beauty of making your own opaline, the fact that you can use a very low amount of phosphate in your formula and then be generous with the amount of rod you use in each piece.

Jordan do you have pics of work made from this formula struck right from the pot? I always made my melts into color bar but it still seemed to strike dense if I took a gather over a cold crack-off moile at about 1.25% phosphate. Never really had to resort to boron or lithium. Replacing the rest of the calcium with barium may be all the fluxing action you need. I was using a wire melter too but never tried those higher %'s of phosphate.

Thanks Dave for that thread a few years back!

Eben Horton
02-13-2018, 05:58 AM
The most beautiful phosphate opals I have seen are ones that look like a cross between Vaseline and mayonnaise. (How’s that for a visual? )
Whites with hints of slightly yellow and reddish hues within.

Pete VanderLaan
02-13-2018, 06:44 AM
It should not strike right from the pot. That would indicate the presence of fluorine. Since a phosphate is a phase separation glass it takes a cooling cycle followed by a heating cycle to cause that occurrence. The curiosity of the stuff Jordan made and I had noted to him privately was that it was streaky, something I didn't like. It looked like someones combed hair.

Marc Carmen
02-13-2018, 07:00 AM
Ohh the streaky part sounds interesting. Do you think the streaks just came from a layer of crud on the surface of the melt?

IMO fluorine totally screws up a phosphate opal but the color makers all seem to be doing it.

Kenny Pieper
02-13-2018, 07:32 AM
I make goblets out of a phosphate opal and usually use the color right out of the pot. Well one day I got an order for a few of the opal goblets that I didn't have in stock so I made them out of a bar I had from the last melt. When they came out of the oven and I set them next to the other goblets I could see the ones made out of bar were not nearly as bright and lively. They were more gray. So now I only use that glass out of the pot. All about the thermal history!

Jordan Kube
02-13-2018, 06:04 PM
Care to pass that one along Kenny? I'd be interested to see how the different chemicals affect that strike. Or if not, maybe compare against Dave's formula for us? I make goblets out of this stuff and barely get anything to happen.

Pete VanderLaan
02-13-2018, 06:17 PM
look at two things. First Sodium tri poly phosphate. break that down.
Then look at trisodium phosphate, Break that down
The look at calcium mono phosphate. Break that down.

Then look at calcium phosphate as a phase separation issue. then look at apatite crystals and why they do what they do. Then count the stones. Then get it really hot and small charges. If you can get rid of the calcium and replace with strontium your day will go better. You can't get rid of all of it.

Jordan Kube
02-13-2018, 07:44 PM
Would the strontium be a 1 to 1 substitution for calcium?

Greg Vriethoff
02-13-2018, 09:11 PM
God, the stuff that I love.

Thank you!

Pete VanderLaan
02-14-2018, 07:59 AM
Would the strontium be a 1 to 1 substitution for calcium?
****
It should be fine if you notice that the expansion factors are so similar.

Jordan Kube
02-14-2018, 03:32 PM
Alright, looks like I've got some work to do. I'm getting closer to a nice copper blue with silver. The third melt is happening today. The erbium glass is now almost dead on in expansion and hopefully will go into production. Second test for that next Tuesday. I'd really like to loosen it up a bit, it's pretty viscous stuff. I'm wondering if our good friend strontium could help?

Pete VanderLaan
02-14-2018, 05:17 PM
My offhand thought is cryolite= sodium alumina hexafluoride/ Very small additives would reduce the melt conditions. It would slop it up. Otherwise sodium nitrate for the runny goblet people. . Either will push the expansion around.
What you need to be seeing is the phase separation reduction of Apatite crystals occurring because the calcium is being dropped. Trying to do this in essentially a production shop is really ambitious.

This is a phrase that really gets spell check maxed out. Now it wants appetite.

Dave Bross
02-14-2018, 05:26 PM
Jordan,

Strontium will help. Lithium will help a lot.

If you have Volf read up on strontium. Similar effects as lead without the toxicity.

Be very sure you have enough alumina with strontium (Volf) as in sum of 1st column in periodic table divided by eight (Labino).

Jordan Kube
02-20-2018, 10:49 PM
I added back half the borax from Dave's original recipe and a little bit of cryolite. I also doubled the potassium nitrate after looking at my other recipes. Small charges every 1.25 hours with a good stir in between each charge. It's looking really nice so far. We shall see.

Jordan Kube
02-21-2018, 05:07 PM
Wow, it's gorgeous. Does exactly what I wanted. Pops right out of the furnace and has that beautiful fiery glow. It is also possible I screwed up my first melt of the 5% somehow, which has always been a thought in my head.

Added half of Dave's borax after reading boron was helpful, added .75% cryolite for same, doubled pot nitrate, pulverized the lithium with the STPP, small charges with stirring to maintain furnace temp as high as possible throughout the melt. There was only a very small patch of scum on the surface, similar in size to a patch of frogs eggs one sometimes gets. Raked off nice and easy. Gorgeous glass underneath. I suspect the patch would not have formed if I had stuck around for an extra hour after I put the last charge in to stir. Just need to adjust expansion now.

Thanks everyone!

Pete VanderLaan
02-22-2018, 07:02 AM
Those patches take forever to go away by themselves. If it's bubbles, I don't rake, I squirt them with a windex type bottle on straight spray.
Given Durk's suggestion regarding the formation of borates as an unpleasant side effect of the borax plus moisture, it makes me wonder if it might be better to use boric acid or anhydrous borax. The boric acid would bring expansion down, something borax really doesn't do. I tend to put the nitrates in a coffee grinder since all of that stuff is prilled now and the things are too big.

I was charging a cobalt silver opal and a copper ruby yesterday and had time to consider Volf on the subject of strontium and it doesn't really quite say it can substitute in part or whole on the calcium but it is clear to me that the less calcium the better if you don't like Apatite chunks. It was wise of you to crush the STP in the lithium. It's a favorite trick.

I haven't tried a copper ruby since I left New Mexico. Doing that with a moly is a futile exercise but with this little gas furnace I'm running now, my old 7,000 feet in the foothills formula was rather intense and a thread the size of a human hair struck very well on the outside of a clear gather, to the point that I cut the copper content in half and still have a red strike going on a punty whereas the goal was to have it strike in the annealer. Making it as a phosphate might be remarkable, sort of like those old Mother of Pearl colors Zimmermann used to make.

Shawn Watt
02-24-2018, 11:23 AM
Pete I would be really interested in hearing more about the copper ruby phosphate. for some reason i was under the impression that because the ruby needs to be reduced so much that it wouldn't work in a phosphate base that has the oxygen. Could you walk me through that?

Pete VanderLaan
02-24-2018, 12:24 PM
well, as I said, making it might be remarkable, so when I get it, I'll remark in better detail. .

In general, your glass is chock full of oxygen no matter what you do. All those carbonates. If you break your glass down in , moles, you can really see it. So you need something there to "reduce" ( make smaller) the 02 everywhere. Black tin works well. So would metallic copper but would be a PIA,

The formula for Tri sodium Phosphate is Na3PO4. Sodium tri phosphate is Na5P3O10 but each one would have oxygen glommed on to it. The old guano was really about 55% calcium and around 42% Phosphorous and oxygen. The theoretical formula for it is Ca5(OH)(PO4)3, but it varies. Real bone ash is hard to find and you really will have a lot of trouble with the calcium in it making apatite crystals which are really gross.

Shawn Watt
02-24-2018, 03:50 PM
When I took chucks class he worked on cad sel colors in a phosphate base. If i remember right he was using mono calcium phosphate to reduce the O2. They turned out really nice i thought. I hadn't thought about the copper ruby until you said it. Looking forward to future remarks

Pete VanderLaan
02-25-2018, 07:14 AM
When I took chucks class he worked on cad sel colors in a phosphate base. If i remember right he was using mono calcium phosphate to reduce the O2. They turned out really nice i thought. I hadn't thought about the copper ruby until you said it. Looking forward to future remarks
*****
do you have a source on the mono calcium phosphate?

Lynn Read
12-19-2018, 10:58 PM
So I melted this 5% opal the other day:

In pounds
Sand 7.3125
Soda Ash  2.38875
Potassium Carbonate 0
Calcium Carbonate 0.4125
Strontium Carbonate 0.675
Zinc Oxide 0.225
Alumina Hydrate 0.3375
Lithium Carbonate 0.075
Antimony 0.03975
Potassium Nitrate 0.075
Sodium Tripolyphosp. 0.93

Total 12.471

Oxides %
SiO2 66.86
Na2O 16.4
K2O 0.327
LiO 0.278
CaO 2.13
MgO 0.006
SrO 4.35
ZnO 2.06
Al2O3 2.229
P2O5 4.95
Sb2O5 0.365

Charged a few scoops at 2300 every two hours. Held at 2300 for 10 hrs and then down to 2150. It came out pretty scuzzy on top like you guys talk about some phosphates coming out. It was also pretty streaky in coloration and cordy looking. It blew out ok and the stuff I made into bar struck out beautifully after being picked up again, as always. As a note, I ground the STPP in a bullet blender in an effort to avoid some chunkies I was getting in the 2.5% melts. It also came out 4 points high after my educated guess on adjustment. Based on that and my percentages I'm thinking at least adding some silica is in order.

Any thoughts on cleaning this one up?

---
Hey Guys, Jordan and Pete,

I have been reading this thread and wanted to ask if you think this Sagahara glass is a Na5P3O10 opal (STPP)? It has so many amazing hues of blue and golds but the density is so slight I would imagine it must be only .5 %- 1% max phosphate. Based on the images that Jordan posted at 5% I would be far to dense.

I want to run some test melts but trying to gain some feedback first. I will be press molding the glass with a wall thickness of 1.2" - 3/4" thick so I need to limit the saturation. I will be cycling the glass through a cold work process and a second firing for my final fire polish. I am sure the duration of heat cycles will effect the opacity with this glass. I am hopeful that I can get a nice pale smokey white.

Any advise would be helpful in regard to % of STPP or strategies to get the shift if warm and cool tones. Maybe it is just the shape of the glass refracting color.

Pete VanderLaan
12-20-2018, 07:51 AM
That density is probably correct. In the STP melts I've done, it is periodically really streaky stuff, almost like a comb was run thru it but if reannealed, it really took on opacity. Press molding will no doubt do something unexpected but the re strikes matter a lot. Streaking seems to be a repeat concern with it. Kenny wrote me about that last week and I really didn't have great insight. Keep the calcium as low as humanly possible.

Dan Vanantwerp
12-20-2018, 09:54 AM
Looks like silver fuming to me. Almost wonder if that's some boro tubing.

So far my attempts have not yielded as much "fire opal" as just opal. The red only came out when overlaying a chalcedony color. Very interesting look.

Pete VanderLaan
12-20-2018, 12:33 PM
I would be very surprised to find that was not a generic phosphate opal actually.

I have a large piece of Mark Peiser's in our bedroom and its a monolithic casting six inches thick by about 30 inches of a Phosphate glass, which is all Mark works with. During the day it changes from translucent white to yellow to blue and then to red.

The thing that was driven into me over the years was how important the modifiers and stabilizers are in a base glass. They totally determine the color with few exceptions. Calcium is not your friend when making color. Neither is sodium.

Jordan Kube
12-20-2018, 06:08 PM
You will probably need to let it cool and then heat it back up after pressing to get any color out of it. You are really going to be able to take advantage of the beauty of this glass with those thicknesses. I would start at 2%

Lynn Read
12-20-2018, 07:56 PM
Thanks for the feedback. It will take me a couple weeks before I can start the tests but if I get any positive results I'll share some photos. Cheers to taking notes.

David Patchen
12-21-2018, 12:14 AM
You might hit up George Bucquet--he makes some beautiful opaline glass.

http://www.georgebucquet.com/

Pete VanderLaan
12-21-2018, 11:14 AM
Always worth remembering where the 5% phosphate content came from. That was out of the 1968 NCECA conference ( pre GAS) where Robert Held established that you could add up to 5% bone ash 21 to your basic clear formula and it would still be compatible with the existing formula. It was never a density guideline.

Bone Ash 21 was a curious true bone ash. Greasy, irregular, maybe bat guano that Standard ceramic supply marketed. They had one box car full of it and that was the end of it. It was profoundly difficult to melt cleanly, taking fine screening and temperatures over 2400F. The formation of Apatite stones was the problem which occur with the introduction of any calcium source. So, having calcium in your basic formula just makes things worse. Strontium as a substitute stabilizer fell into use but the number of people melting this stuff was tiny. Mark went into it immediately and has yet to depart and continues to get best results with Calcium monophosphate which is incredible difficult to obtain. Sodium tri phosphate works most of the time with some inexplicable deviations and so does Tri Sodium Phosphate which puts a lot more sodium in the melt.

If one accepts the notion that sodium and calcium are not your friends in this type melt due to the stones AND the color, then going to sourcing such as potassium nitrate and strontium carb would draw you in. Dumping as much calcium as possible is a step in the right direction. If I had any major criticism of the formula Jordan offered up, it's the sodium content. I haven't melted a phosphate opal in years but I would certainly think hard about switching alkaline fluxes. Bathe the STP in the lithium if you use a little and that would help as well.

Jordan Kube
12-21-2018, 07:00 PM
Mono Potassium Phosphate would perhaps be a good choice then Pete?

KH2PO4

Pete VanderLaan
12-22-2018, 07:37 AM
I have no idea. You need a little calcium. Emphasis on little. I don't actually know the structure for such a material. (PAUSE)
OK, here's calcium monophosphate: Ca(H2PO4)2 divalent
Here's potassium phosphate: K(H2PO4) divalent

phosphorous : valence 5
Phosphate combo valence 3

worth noting in the pentavalent form (Ca5) it appears to grow apatite, not your friend unless you love bone snot.

So armed with that info, I think it might be worthwhile to try it although it sounds like a fairly obscure compound to be found in your average chem supply warehouse. I think that really breaking it down would take a trip into mole chemistry. Count your atoms.

None of this clarifies much for me. Melt some.

Jordan Kube
12-22-2018, 01:56 PM
A little obscure, sure. Food and fetilizer chemicals. Not our usual source for supplies. I was able to find the Pot phosphate in 50# bags for $2.38/# delivered here https://www.greenwaybiotech.com/collections/water-soluble-fertilizers/products/monopotassium-phosphate?variant=1557348161

I could not say the same for the Cal monophosphate. It is a pretty common food additive so someone has it for cheap.

You know me Pete, I'm always happy to try something rather than speculate. Thanks for the breakdown.

Pete VanderLaan
12-22-2018, 03:36 PM
I was unsuccessful on the Cal monophosphate which surprised me so I went with the STP and have 100 lbs which will take me to the end of the line. The STP does inexplicably streak, even to the point of leaving what look like fingerprints at times. On a reanneal, it's dense and has great color. The trouble I see with the fertilizer grade is the tramp stuff.
It turns out your bones are largely apatite in the pentavalent state. A state you want to stay away from. Right now, I'm melting copper blues and they are so stunningly beautiful and so stupid easy.

Report back on the pot phosphate. It's a very interesting idea. That's not a terrible price although getting it back east might cost.

Jordan Kube
12-22-2018, 05:15 PM
Free shipping.

I'm not currently melting batch but I do have a place in mind that might accommodate me. If I wasn't so taken with machining at the moment I'd probably have a little test furnace going by now.

Yes to the copper blue. Really the most beautiful blue out there, isn't it?

Pete VanderLaan
12-23-2018, 08:10 AM
I think it's eye popping. Make it with potassium and barium!

As to the pot phosphate: It's likely it will come to you "Prilled". I don't care for prilling since it's hard to mix in. I have to run all that stuff through a grinder and I would imagine that Phosphates will really need fine grinding. Bathe the junk in the lithium.

Clearly you need a glass melter in the CNC shop.

Lynn Read
01-03-2019, 02:38 PM
So far my tests are not producing the results I want.

My batch is Spruce Pine W/er 87. I have tried STPP at 2% and not visible white showing. It is melting clean at 2350 but I am only melting small 50 lbs tests.

My next test will be is to increase the STPP to 4% and see if it shows. I may then test with Nono calcium Phosphate. Some people say it is much easier to melt with S. P.

Am I way of the mark to achieving a low density opal white using Spruce Pine?

Pete VanderLaan
01-03-2019, 05:56 PM
5% would give results but it does matter where the bone ash came from. I've had some good results from STP and some from commercial Calcium Phosphates which did nothing. I assume a type Not Nono but Monocalcium phosphate but the synthetically derived stuff did nothing in my work ever.

It is not one of those glasses that gives you instant gratification, far from it. Calcium makes life Ugly. SP has Calcium.

Dave Bross
01-03-2019, 07:13 PM
Way too much calcium in SP.

This is one glass you have to batch from scratch due to the calcium being required to be a very low percentage.

It's worth the trouble to mix it up as batch. Instructions and how to for small amounts are further back in this post.

Pete VanderLaan
01-04-2019, 06:55 AM
Empowering yourself doing it is worth the trouble. I still remember the first day I mixed a raw formula. It was Dudley's. Just an amazing feeling to realize that you really can do this. At that time, I mixed in an open barrel with my hands.

It opens up your world.

Eben Horton
01-04-2019, 09:01 AM
Empowering yourself doing it is worth the trouble. I still remember the first day I mixed a raw formula. It was Dudley's. Just an amazing feeling to realize that you really can do this. At that time, I mixed in an open barrel with my hands.

It opens up your world.

Well.. the recipe obviously said “mix well by hand”

Pete VanderLaan
01-04-2019, 09:24 AM
It's really a great way to start. You can buy 20lbs of the materials at any pottery. You need a decent scale and a bucket. Mixing with your hands really does work, not as well as a mixer but it works. It just lets you know you can make your own glass.

To me, that's empowering.

You need Silica, soda ash, Potassium carb, calcium carb ,sodium nitrate and some antimony oxide. The antimony may not come from a pottery but Universal pigment certainly has it. Mix a formula, throw it in a pot that's at least 2200F, let it melt and go flat, add more, wash rinse repeat. It takes about 8 hours after the last charge. Keep it at least 2200F. You'll have glass the next day. Add metallic oxides for color at about .1 percent max.

Art Freas
01-04-2019, 09:40 AM
Wonder if one of these would work for mixing.
https://www.amazon.com/Scepter-04239-7-Gallon-Odjob-Mixer/dp/B000BPK766/ref=cm_cr_arp_d_bdcrb_top?ie=UTF8

Pete VanderLaan
01-04-2019, 12:46 PM
Henry Summa initially used something much like that in the early days when he was in New York. Cheap, fairly effective, takes up no space. Our little 7 inch crucibles don't cost much and if you prefer, Assay pots cost even less. My first pot furnace was built in a 55 gallon drum sawed off with a kast-o-lite 30 lid. Really low tech.

As to the mixer, the proof is in the pudding. It melts or it doesn't or something in between but the glass is talking to you. If you consider the cost of color rods compared to the cost of DYI , you'll be floored. Further, you'll make glass that doesn't look like everyone else's. The copper blue I'm using right now is absolutely electric and incredibly simple.

Read the stuff I wrote in Glassnotes IV on batching. It's a simply guide to doing it.

Lynn Read
01-05-2019, 01:41 PM
You might hit up George Bucquet--he makes some beautiful opaline glass.

http://www.georgebucquet.com/

Thanks for the Suggestion. I talked to him last week and he had some great advice and using MCP. Mono Calcium Phosphate.

Lynn Read
01-05-2019, 02:13 PM
I wanted to share the results from my tests melting Phosphate white.

I am working with Spruce Pine Batch W/er87. Melting in an electric furnace with 50 lbs test melts at 2350 for about 4 hour melt, drop to 1900 for 4 hour soak and back up to working at 2130. That can be adjusted I think.

First tow melts with STPP Molecular FormulaNa5O10P3 Did not have any visible opalescence. My third test worked but was not an ideal system.

50 lbs SP batch
907 g STPP

Image #1 Full reheat - After a started Bubble is allowed to cool, the second gather and a full reheat caused the density to develop.

Image #2 Fresh gather cast and pressed. no reheat

Image #3 Spot heat with hot torch. My favorite so far

Image #4 started bubble allowed to cool and gathered with a limited reheat

Image #5 Spot heating with Torch on cast glass.

Amazing the variation heat has on this glass.


Does anyone have recommendations on getting the phosphate to strike on the cool down vs the reheat? I want to use this is casting /press molding but I do not have the option of reheating my castings without loosing the shape and texture. See image 5 for best results.

Pete VanderLaan
01-05-2019, 04:31 PM
What Mark did in the "Ladder to the moon group was to cast the basic phosphate material and then press a "ladder into that mold. That caused a chill. Then the casting continued and the interface was opalescent.

Jordan Kube
01-05-2019, 07:53 PM
Bravo Lynn! That's the stuff!

Try removing your pieces from the mold after they've chilled and then hitting them with a hot torch on a turntable before boxing. Intense heat that won't necessarily cause you to lose your form.