[Darkroom] Granite Counters

Chris Murphy chrisnoisebridge at gmail.com
Sat Feb 6 18:58:53 UTC 2010

This is just a guess, granite is nowhere near radioactive enough to be  
a concern around film. The exposure time with direct contact to  
granite would probably be months with high speed film. Again, I'm just  

As a boy, I measured the radioactivity of granite buildings and found  
no significant levels above cosmic and solar background radiation.  
Smoke detectors contained americanium and were much more interesting  
to measure.

Apparently old lenses contain thorium and yttrium and even those would  
take several weeks to expose ISO 100 film.

We could intentionally expose ISO 6400 film to granite in a light  
tight photo paper box and see what happens vs a clipping of the same  
roll that has not been exposed. A Geiger counter could be used to  
calculate a proper exposure time?


Sent from my iPhone

On Feb 5, 2010, at 16:30, Jasmine Strong <jasmine at electronpusher.org>  

> I'd be touchy about granite for a darkroom on the grounds that it can
> be surprisingly radioactive and that this can fog film over time.
> -J.
> On Feb 5, 2010, at 3:46 PM, John Magolske wrote:
>> * Kelly <hurtstotouchfire at gmail.com> [100205 15:37]:
>>> Well, just to be clear on our options here, what are our  
>>> requirements
>>> for a counter surface?  (Ben?)  What are our other price options?
>>> -Stainless steel (also not cheap)
>>> -Formica (cheapest option--price estimate?)
>> I've heard soapstone is ideal for chem-lab counter tops (more inert
>> than granite, etc.). I'm not suggesting we should hold out for that,
>> but if there happens to be a big slab of it laying around  
>> somewhere...
>> It's also easy to cut.
>> John
>> -- 
>> John Magolske
>> http://B79.net/contact
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