Chemical grade questions

[aaron2]

In the Albumen & Salt Paper book, it is mentioned that a "technical"

or "ACS" grade is sufficiently pure and there is no need to purchase

the highly purified grades that are required in photographic emulsion

making.

But in The Darkroom Cookbook, it is said that AR quality which is

labeled "ACS" meets the highest standard for purity and

uniformity. "Technical" grade is intended for manufacturing processes

and is generally not recommended for photographic work.

 

I am looking to buy some raw chemical for photographic processes and

these information about chemical grades lead me no where. Do I use

different grade chemical for different stages of photographic

processes? Is the term "Photographic" grade understood by the

chemical house?

 

Here's what I need:- Sodium Thiosulfate (Penta), Ammonium

Thiosulfate, Sodium Sulfite, Sodium Metaborate (Kodalk), sodium

Citrate, Borax, Gold Chloride solution.

 

Thank in advance for your contribution.

[marco_maria_colombo]

Hi Aaron. A brief explanation of the chemical purity grades can be found it <a href="http://www.mallchem.com/catalog/grades.asp">here</a>, while I believe that the major chemical firms don't specify any "photographic grade", although I've checked the Sigma Aldrich catalogue where, under the name Potassium ferrycianyde, it reports "99 % purity, for photographic applications". That's my cent -- Ciao, Marco.

[light-zone]

Hi Aaron,

 

Photographic Grade or quality will be understood by the chemical distributors. The difference in the grades usually has to do with either purity or water content.

[robert_davis2]

I've bought virtually all of that from Fotochem [borax from the grocery store and I've not needed gold yet I'll buy the vit C from the health food store]. Fotochem sells to people doing photographic so he knows what standards are needed. I'm amused by the statement that techincal grade is for manufacturing processes and not good enough for photographic uses. Isn't Kodak a manufacturer? So does the chemical change it's purity when Kodak gets hold of it? Maybe some chemicals have higher requirements? I don't know but with some of this stuff it wouldn't surprise me if techincal grade is photographic grade.

 

http://www.colba.net/~fotochem/

[light-zone]

The Online vendors for chemicals that I use do mention photo grade, (like I said above) (http://www.Carl-Roth.de/) but what is interesting is, the photo grade is usually cheaper, thereby implying either a higher moisture content or possibly a high degree of impurities. Either way, I choose the photo grade which is cheaper and has worked thus far.

[aaron_van_de_sande]

The chemicals you mention are high-tonnage chemicals and the processes are so refined that even the standard grades are very pure. I wouldn't get hung up on it.

[aaron2]

Robert,

What the book refers to as "Technical" grade actually implies laundry soap, etc.. I'm quite sure they don't mean Kodak in this case. I should have mentioned it more clearly in my initial post. Thanks.

 

Marco,

Thanks for referring me to the website. Just what I needed...but I'm more confused now that so many more grades has popped out. Which grade from the list should I be looking at for my needs. There's a "Practical" grade in this list, and Steve Anchell mentioned in the book "Practical" grade should be good for most photographic purposes.

 

Many Thanks.

[aaron2]

William,

"Photo" grade isn't understood by chemical suppliers in my area. The prices quoted to me here is about 500% higher than what I can get from photo chemical suppliers in USA. I guess the grades I'm quoted here are much purer than what I need. So I'm still wondering how to describe to them the right stuff.

Thanks.

[ole_tjugen]

I'm not too concerned with the grades, I just try to find the cheapest package. If I have to choose between 1kg "Photopur", 10kg technical or 10g "pro analysi", I will choose the amount closest to what I need unless the larger is much cheaper. So now I have 1kg hydroquinone, even if 10kg was a little cheaper.

[robert_davis2]

Check the section on Borax in "The Darkroom Cookbook" he basically suggests getting it from the laundry section of the grocery store. He also suggest something similar for lye [sodium hydroxide? I forget] and TSP. Then there are the chemicals from the pool supply aisle. The next time I need potassium bromide I'm going to try the stuff for hottubs. It isn't cheaper then the place I order from but it's easier then waiting for the shipment and to boot I think the website claims a pretty high purity for the stuff.

[aaron2]

Thanks again, Robert, for the information. Thanks to all.

[light-zone]

Aron,

I am in Germany, and when a chemical is labeled as "photgrade" it is inevitably the least expensive of all.