[glassy24]

Can anyone help me find an answer? i'm a glass artist and lately i have been working on creating fluorescent glass color using fluorescent minerals. every one i have tried so far ends up being compatible with the glass but no longer fluoresces after its been heated (to about 1900-2100 degrees fahrenheit). I know of some phosphors that are able to withstand temperatures of at least 1300F but they "burn out" at the temp i'm working with. What physical property/properties should i look at to figure out if the minerals can withstand high temperatures and still fluoresce, melting point, flash point? and what actually causes them to stop fluorescing? does the molecular structure actually change at a certain temperature? also, the mineral powder is encased in glass, i know many forms of phosphorescence require interaction with oxygen but does the lack of oxygen effect fluorescence at all? I hope im posting in the right forum, if anyone can answer any of my questions or even direct me to a good source of information on the subject it would be greatly appreciated, thanks!

[Enthalpy]

Welcome here, Glassy24!

I'm no expert on fluorescent materials, but here are my two cents worth of answers, until someone more knowledgeable jumps in.

Some fluo materials are organic and these wouldn't survive the heat. Most mineral fluo materials should survive 1100°C. However, I imagine a few mishaps that can occur:
- Glass impurities, especially sodium, diffuse at heat into the fluorescent material. Fluo materials must be sensitive to contamination, because their desexcitation path that emits light is fragile, and contaminants offer competitor paths for desexcitation.
- I expect fluo materials to work only at a minimum grain size, and mixing into the glass may have dispersed them at atomic scale.
- Glass stops hard ultraviolet, so these wouldn't reach the fluo material. What excitation wavelength do you use?

There are fluo materials that work within a transparent ceramic matrix, hence operate after a hot process, and they're used to produce lasers, for instance Cerium atoms in Yttrium-Aluminium-Garnet - but these materials (these dopants) are meant from the beginning to operate in this particular matrix, not as bulk material.

Such potential explanations would lead to trials which are time-consuming: mix the fluo material less well with the glass and cool earlier; try silica instead of glass; try the bulk fluo material behind a pane of glass...

[glassy24]

Thanks for the reply, unfortunately some of the answers were pretty much what i expected. Im using LW uv, between 390-425 since the glass is going to be used for a sculpture i don't want to use a shorter wavelength as it would be bad for the viewers eyes unless they wear protective glasses, also, good SW lamps are pretty expensive. the glass is not filtering the uv too much, i have tested the minerals through glass before each use, and unfortunately cooling the glass faster is not an option since it will cause the glass to crack, (its "soft" glass or "soda-lime" not borosilicate) also mixing the glass less creates incompatibility, i have tried that a few times. lastly i cant use only silica since i need this glass to be compatible with the glass im melting in my furnace, so i would have to mix it with that glass, all great suggestions though and much appreciated. im interested in the idea of some materials becoming fluorescent after heating/bonding with the glass (if that was even what you were getting at with the ceramic matrix). if you could elaborate on that it would help a lot! i do use uranium glass a lot in my work that is made with uranyl salts which become fluorescent bonding with the glass, if you have any suggestions of other materials that may react in a similar way that would be great! thanks again for your reply, hope to hear back from you again

[curiouscat]

Wikipedia revealed:

"certain impurities such as iron or copper need to be absent, to prevent quenching of possible fluorescence."

Have any of that in your mix?

Also, try adding Divalent manganese, or Trivalent chromium.

[glassy24]

nope, no copper or iron, the glass i use is "soda lime" or "soft glass", the batch is a mixture of silica sand, soda ash, and lime. thanks for the info, ill definitely give those a try

[Arkcon]

You may need specialty glass.  Much of the soft or soda-lime glass contains an iron impurity, giving it a greenish cast (i.e. plate glass, window glass.)  In general, a trace of other minerals are added to "redden" the green so the human eye can't discern it.  If you're going to do fluorescence with glass, you will have to tell your supplier so, so they can sell you glass formulated appropriately, but it may be expensive.

When I was working with laser fluorescence, in the visible using lasers, we had two types of glass:  straight up, cheep, window glass, used basically for sizing and identifying the shape of things that would go into the device.  It had a noticeable green color, when viewed from the side of the sheet.  For actual use under the laser, we used Tempax^(tm), a grade of Pyrex glass, it  was clear when viewed from the side.  But you will find that difficult to melt in an art furnace.

[curiouscat]

You may need specialty glass.  Much of the soft or soda-lime glass contains an iron impurity, giving it a greenish cast (i.e. plate glass, window glass.)  In general, a trace of other minerals are added to "redden" the green so the human eye can't discern it.  If you're going to do fluorescence with glass, you will have to tell your supplier so, so they can sell you glass formulated appropriately, but it may be expensive.

Alternatively if you could melt the glass and find a way to remove the iron impurities. As oxidation products or slag.

Would blowing air help? I have no clue.

[glassy24]

thanks for the response, the type of furnace i use already has an air blower, it runs on natural gas and the blower helps it reach and maintain a temp of around 2050F, boro is workable around 3050-4000F so its extremely hard to keep molten in a furnace, though it is possible and iv seen videos of it. the glass i use is a higher quality than window glass or "float" glass which is actually poured out and floated on a bed of molten tin which gives it its greenish hue. i use spectrum or system 96, its formulated for blowing glass and is optically clear, while not as dense as crystal it still looks clear when its poured in thick blocks or when a blown piece is cut in half and viewed from the side. i think the main issue im having is less about impurities and more about the temp being too high for these complex fluorescent molecules maintain their structure. if anyone has any suggestions of fluorescent materials that can be heated over 2000 degrees and remain fluorescent or materials that may become fluorescent after being heated or bonding with the glass that would be very helpful. Im learning a lot from all of these replies thanks again. (also, where might i be able to buy divalent manganese and what is the difference between that and manganese dioxide?)