The DARKROOM COOKBOOK, Third Edition

Safety in Handling Photographic Chemicals 161
However, fi ne dust and powder, whether it is mercuric chloride or sodium carbonate,
an ingredient sometimes found in food, can be damaging to the sensitive membranes of the
sinus and lungs. For this reason, the minimum precaution for mixing dry chemicals is to use a
dust mask available in hardware stores and only mix in a room with good ventilation. If a dust
mask is not available, mixing the chemicals outside is another option, though even outside a
dust mask is a good precaution.
The Submersion Method
A safe method for mixing prepackaged dry chemicals is one proposed by Richard Henry in
Controls in Black-and-White Photography. Henry suggests cutting the top of the packet
completely off with a pair of scissors then immersing the entire packet under water with
a gloved hand. It is important to use a mixing container with an opening large enough for
one hand. It is important to have enough room to hold the packet under water and move it
around to dissolve the contents.
This method can also be used with chemicals which have been weighed on a scale.
Weigh the chemicals in a plastic container, available from chemical supply houses, and simply
immerse the entire container—don’t pour. A dust mask should still be used while removing
the powders from their storage containers.
CHEMICAL STORAGE
Keep all chemicals away from children and pets. If necessary, lock the chemicals up. Label and
date all bottles of mixed solutions. Do not use drink or food bottles for darkroom solutions
that are not clearly relabeled. Be sure storage bottles have a secure cap. Protect all chemicals
from air, heat, light, moisture, and contamination from other chemicals.
DISPOSAL AND SAFETY
When working with any chemical, you must assume the responsibility for its safe use and
disposal. Follow any special instructions included with each chemical or process being
used. Laws concerning disposal of chemicals vary widely. Contact the hazardous materials
(HazMat) unit of your local fi re department. They will explain in detail exactly what you can
and cannot do in terms of disposal in your area.
Some noncorrosive liquids can be poured onto cat litter and placed in a plastic bag.
Often, dry chemicals or contaminated materials can be disposed of by sealing them in a plastic
bag. These should be left in a closed, outside dumpster. Do not mix liquid and solid waste
together, as dangerous reactions might occur. Be sure to read and follow all safety recommendations
that come with the chemicals.
ADDITIONAL INFORMATION
The Offi ce of Radiation, Chemical and Biological Safety of Michigan State University, (517) 355-0153;
www.orcbs.msu.edu.
Oxford University’s Physical and Theoretical Laboratory, www.physchem.ox.ac.uk/MSDS.