Using geothermal silica

[Astro Adri]

Hey,  I work in a geothemal power plant.  I can get my hands on some sillica scale that comes from the wells.   I put a lump in the kiln at 1200C, instead of melting like i thought it would it came out as a crumbly white product.  Has anyone got any suggestions as to what I may add to get it to behave more like glaze/ glass.  

Thanks 

[BobMagnuson]

Are you sure it's silica scale?  If it's lime scale, CaCO3, heating it up will convert it to CaO, or quicklime. That's easy enough to test, because quicklime will get very hot when added to water.  I'm not familiar with geothermal wells, but scale in water wells is usually mostly CaCO3 with some some MgCO3 and a little SiO2.

[Min]

If it is silica then it won't melt at 1200C. Typically are there fluxing minerals in the scale also? 

[BobMagnuson]

Scale from water wells will not have any significant R2O.  CaO is a flux but CaO-SiO2 alone won't melt until well over 2000 C.

[Astro Adri]

Fairly sure that it will be a sillica scale.  Calcium based scales wouldnt form in well it was near ( not enough CO2).  Could try putting some acid on the original and the baked product.  There were other minerals present... as it had some black/grey hues, so most likely lithium/manganese.  I may get one of the lab techn to pass it under the xrf and see whats in there.  Was thinking thay i may need to add some sort of Flux but wasnt to sure what.  

[Min]

Is this the type of silica scale you have? (Google image)

I'm wondering about particle size and how you would get the silica scale into a useable mesh size without specialized equipment. With many glazes having a 325mesh silica versus 200mesh makes a difference in the melt. If you can get around that problem safely then to make a glass I'm thinking soda lime glass from soda ash + calcium carb + silica might be a good experiment to start with. 

[Kelly in AK]

You got lab guys there, xrf instruments!? Lucky. I’m mostly out of my league here, but I like @Min’s thought. Perhaps try a soda ash+CaCO3+ “mystery material” triaxial blend. Then there’s borax/boron, which seems like it would flux anything and is a glass former too. 

[Astro Adri]

Hi Min,  simlar but different. Unfortunately i cant get a file small enough to attach here.   That looks like it was formed at atmospheric pressure.  The stuff i have was formed at about 5 to 8 times that so doesnt look 'fluffy'.  Think something simlar to obsidian in texture.  

Hi Kelly in Ak yep we have a lot of toys... well the lab does us field ppl no so much.  Will give that a go.  Got any suggestions on ratios or just follow a basic glaze?

Thanks 

[Kelly in AK]

I don’t really have any idea, I think looking at glaze recipes is a start if your aiming at using the stuff in a glaze. If you’re looking to make straight up glass, here’s a clip from Britannica:

“soda-lime glass, most common form of glass produced. It is composed of about 70 percent silica (silicon dioxide), 15 percent soda (sodium oxide), and 9 percent lime (calcium oxide), with much smaller amounts of various other compounds.”

[Min]

On 11/18/2022 at 12:13 PM, Astro Adri said:

Unfortunately i cant get a file small enough to attach here

If you email yourself the picture it should resize it smaller then try posting that one. 

On 11/18/2022 at 12:13 PM, Astro Adri said:

Think something simlar to obsidian in texture.

How would you get it to glaze or glass mesh size particles?

If you are firing your kiln to glaze temps anyways it would be neat to see what it does in one of your regular glazes, I'ld just swap the silica in a recipe with this silica scale (if you can powder it down safely) and see what it does. A clear maybe? And for sure fire it on the inside of a bowl since we don't know what will happen to the melt.