Hello,
I bought some whiskey stones on Amazon to weigh my hop bags down during dry-hopping. They looked like glass on the listing and (okay i didn’t read it thoroughly), turns out they are made of grainte.
It should be fine if they are polished. When I used to use hop bags I used glass marbles. They were easy to come by and sanitize. Remember to give your bag lots of extra room to swell. As the hops absorb beer they appear to quadruple in size and as they do will choke out the hops towards the center of the bag reducing contact.
There is a possibility that you will see some reaction over a period of time. From wikipedia…
The reactions as follows:
CO2 + H2O → H2CO3
carbon dioxide + water → carbonic acid
H2CO3 + CaCO3 → Ca(HCO3)2
carbonic acid + calcium carbonate → calcium bicarbonate
Chemical weathering of granite occurs when dilute carbonic acid, and other acids present in rain and soil waters, alter feldspar in a process called hydrolysis.[14][15] As demonstrated in the following reaction, this causes potassium feldspar to form kaolinite, with potassium ions, bicarbonate, and silica in solution as byproducts. An end product of granite weathering is grus, which is often made up of coarse-grained fragments of disintegrated granite.
I thought whiskey stones were the fight inducing side effect we irish get after a night at the pub…
Well played @dannyboy58, thanks for the laugh. 
@RenegadeSnare I bag my hops in my keg in a muslin bag and have never weighted them with anything. I also leave them in for the duration until I kick the keg. Then my kitchen trash can smells AMAZING for a while, just not according to my wife 
. I try to be considerate and change out kegs close to garbage night.
Rad
chemistry class 101.
I found some ceramic egg ups so i think i’m gonna use them, just incase!
the room i will be fermenting in is 17C - do you think this will be a problem for an IPA?
That’s what…62F? That’s about perfect for most ale yeasts.
I would make sure they are completely glazed. If not the untreated portion will soften, absorb beer, and likely leave an off flavor.
I don’t think you need weights.
When I used paint strainer bags I would sometimes put some small stainless hose nipple or whatever was lying around in the sack with the hops. Other times I’d forget. Never noticed any difference. I don’t think weight are necessary either but if you use something I’d keep it simple
