Part II Overview: The Photographic Chemistry Laboratory

Four things go wrong in a home laboratory and they are not equally serious. You can be hurt. The people and animals you live with, and the water everything eventually reaches, can be harmed. The materials can be ruined. And the result can be one you cannot repeat, which wastes the most time and is noticed least. This part is arranged in that order, because a control that protects you usually protects the print as well, and the reverse is not true.

Why discipline comes before chemistry

Part I asked you to open a box of paper and carry it into the sun; nothing was weighed, dissolved or poured. From here on every page has a solution in it, and a solution has a concentration, a container, a shelf life, a waste stream and a way of getting onto your hands.

HSE’s guide to working with hazardous substances makes the point this part is built on: risk is a property of the task, not of the substance. The same jar is a small matter when a little is handled with no chance of escape and a larger one during clean-up, when the substance is loose and the operator is tired. So the room, the person, the label, the shelf and the waste bottle come before a single reaction.

The three strands

Part II, and where its nine pages converge

1. 1Laying out the laboratory — wet and dry areas, ventilation, one-way workflow
2. 2Protecting yourself — hazard against risk, gloves, eyes, eyewash, spills
3. 3Reading a safety data sheet — GHS, CAS numbers, your own labels
4. 4Storage and incompatibilities — segregation, containment, shelf life
5. 5Silver nitrate — the one reagent whose rules govern the others
6. 6Waste — streams, silver, and the drain that is not a disposal route
7. 7Measurement and uncertainty — mass, volume, temperature, density, and how wrong you are
8. 8Concentration and dilution — the arithmetic every formula assumes
9. 9Commissioning your laboratory — the lab in which all three strands are used at once

The safety strand is six pages long because most of what can go wrong is not chemistry.

What “laboratory” is allowed to mean

A kitchen after supper, with the food put away. A spare room. A garage bench. A folding table and a box that goes back in a cupboard. Kodak’s guidance for amateurs said the same in 2005: a temporary darkroom in an easily darkened kitchen is a real one, and the kitchen is the most convenient because the water, the drainage, the light and the working surface are already there.

Negotiable: whether the space is permanent, whether the bench is built or borrowed, whether there is a sink in the room, what you spend. Not negotiable: a division between where powders are weighed and where liquids are poured; air that moves; a surface a spill cannot soak into; containers and utensils that never return to food use; a label on everything; and the safety data sheet for every product on the shelf. The next four pages are those five requirements in full.

!This course does not own your local rules

Waste rules, plumbing rules and what a landlord will accept are local, and they change. Every page that produces a waste stream gives the chemistry, gives general practice, and says that your local regulations govern. ILFORD’s guidance for domestic users points United Kingdom readers at the household waste and recycling centre and tells everyone else to find out what applies where they live. That is the shape of every disposal sentence in this course.

Accessibility, stated at the front

Five constraints come up repeatedly, and each page states its route rather than leaving you to improvise one.

• No dedicated room. The layout page gives the box-kit and folding-bench routes and the ten-minute pack-down that returns the space to the household.
• Limited ventilation. The layout page separates what air movement has to achieve from how you achieve it, and says which arrangements are not acceptable.
• Cannot handle certain substances. Buying liquid concentrates instead of mixing powders is a recognised control rather than a compromise: Princeton’s guidance for photographic studios recommends liquid chemistry wherever it exists, because weighing powder is the step that puts a substance into the air.
• Limited mobility, cannot lift or reach. Working heights, decanting from a heavy container into a small one, and mixing smaller volumes are on the layout and measurement pages.
• Colour vision, low vision, tremor. Every label carries written text as well as any colour code, and measurement is taught with whichever instrument reads most finely for the money rather than the most traditional one.

Repeatability is an artistic instrument

A print is a decision about a picture, and you can only read the decision if nothing else moved. Change the dilution deliberately and you learn what dilution does; change it on a day when the temperature also drifted and the fixer was older, and you have learned nothing. This part exists so that the one thing you changed is the only thing that changed, which the art track needs as much as the science track.

Three habits that start here

The lab notebook: what you did, with what, when, at what temperature, and what you saw. The labelling scheme, on every bottle you fill: substance, concentration, dates, hazard wording, initials. The calibration log, in which each check of an instrument against a reference is recorded with its date, so that a suspect result later has a history to argue with. All three are opened in the closing lab.

What to have before you start

Stage 0 of the laboratory planner is the safety and chemistry set: gloves, eye protection, an apron, dedicated containers and utensils, a balance, graduated cylinders, a thermometer, storage bottles, labels and an eyewash bottle. What you need is the short version; the planner is the itemised, dated, priced one. No lesson quotes a price, so prices can be corrected without rewriting pages. Read the page that uses an item before you buy it.

What this part deliberately leaves out

Building a darkroom, with its light traps, plumbing and carpentry, is Part XVI. The first tray sequence and the first developed negative are Part IV. Designing an experiment is Part IX. Recovering silver from spent fixer is Part XII. And the chemistry of why — what a developer is doing, why sulfite is in it, what pH changes — is Part III, which comes next. This part is discipline and measurement: it puts the instruments in your hands and the habits in your head, so that the chemistry has somewhere to live.

What you need first

Only Part I, which assumed nothing. What comes after leans on individual pages here: every practical page assumes the layout, protective-equipment and storage pages; every formula assumes the concentration page; every emulsion and alternative-process part assumes the silver nitrate page; every page with a tray in it assumes the waste page.

The pages of this part

Part2 of 28Level1 — FoundationPages9Estimated time6.0 hoursHighest safety levelLevel B

0 / 9 lessons in this part completed

• LessonLaying Out the Laboratory: Wet Areas, Dry Areas and Contamination Control35 min
• LessonProtecting Yourself: Hazard, Risk, PPE and What To Do When It Goes Wrong40 min
• LessonReading a Safety Data Sheet: GHS, CAS Numbers and Your Own Labels30 min
• LessonStorage, Incompatibilities and Secondary Containment30 min
• LessonSilver Nitrate: The Reagent That Sets the RulesB25 min
• LessonMeasuring Mass, Volume, Temperature and Density, and Knowing How Wrong You Are40 min
• LessonConcentration and Dilution: The Arithmetic Every Formula Assumes40 min
• LessonWaste: Streams, Silver, and the Drain You Must Not Use30 min
• LabLab: Commissioning Your LaboratoryA90 min