Black residue from hard rubber tanks

[Brian Sims]

I have used hard rubber Kodak tanks to develop 4x5 film for decades. I'm about ready to develop some important work so I thought I'd clean up. I scrubbed the tanks with a nylon scrub pad and now there is a black residue that doesn't seem to rinse off. It's almost like carbon black...which may be what they colored the rubber with. The question is: is this going to cause me problems. I'll be running a few sheets through as a test, but that may not show up any problems due to contamination that may affect sheets in additional batches. Anyone dealt with this?

[Donald Qualls]

I had a similar coating in some black hard rubber developing trays; in mine, it scrubbed off nicely with mild soap and a wet paper towel. I wouldn't recommend scrubbing those with an abrasive-loaded pad like Scotchbrite, because it can scratch the rubber surface, which might cause the surface to retain chemicals (i.e. make it harder to wash). You could, however, polish it with something like Bon Ami (on a soft cloth, cellulose sponge, or paper towel) to try to both remove the residue you see and smooth out any scratches already on the surface. Bon Ami uses calcium carbonate as its polishing agent (plain, ordinary, but very carefully purified, chalk), and a standing rinse of half an hour with stop bath will dissolve all traces of the Bon Ami after an ordinary water rinse to get the soap/detergent component out.

[Brian Sims]

Thanks Donald. I give it a try.

[Turner Reich]

Donald is exactly right, don't scrub it with an abrasive pad, you don't want to scuff up the surface but just want to wipe off the residue.