Reviews
Anthotype Pigment Testing: A Logbook Method for Comparing Plant Exposures
Build a repeatable anthotype logbook: coat test strips, score fade against a fixed patch, and compare plant pigments side by side before you coat a full print.
What to take away
- One logbook page per batch, listing plant, mordant, paper, coating passes, start time and hours to each fade step.
- Every test strip runs beside a control strip of the same paper, so sun and weather hit both equally.
- Fade is scored against a fixed reference patch, never against memory.
- Paper, coating method and frame stay constant for a season, with one variable changed per run.
The Case for a Written Logbook
The hard part of anthotype pigment testing is not coating paper; it is recalling what you did three weeks ago.
The anthotype process works because sunlight destroys a plant emulsion slowly enough to leave a tone behind.
Without a written record, two strips that faded differently look like luck rather than a result you can repeat.
Names matter too. Two jars of the same berry picked in different weeks are different batches, and the log should treat them that way.
A notebook with columns beats a camera roll, because the camera records the end and the notebook records the middle.
Test Strip Setup on a Single Sheet
Sun printing covers several contact processes, and the frame you build for one serves the others.
- Cut one sheet of the same paper into equal strips, at least five per pigment, and label each with a pencil code.
- Coat each strip with a fixed volume of strained emulsion, using the same brush and the same number of passes.
- Dry all strips in the dark for the same interval, then store them in a light tight envelope.
- Expose a control strip and one pigment strip side by side in the same contact frame, at the same hour of day.
- Lift one strip per pigment every hour, dry it flat, and photograph it beside a grey card.
A Comparison Table for Fade Results
Copy this grid into a notebook or a spreadsheet, one row per strip.
| Field | What goes in the cell | Why you keep it |
|---|---|---|
| Batch ID | Beet 04, picked 12 June | Separates pickings of the same plant |
| Coating | Three thin passes, one brush | Shows whether density drifted between runs |
| Start | 09:40, clear sky | Ties fading to light rather than the clock |
| First change | Patch edge softens | Earliest sign of plant pigment lightfastness |
| Patch match | Strip equals patch four | Gives anthotype exposure times a fixed target |
Paper and Emulsion Variables Worth Pinning
Paper sizing decides how much emulsion stays on the surface, so switching brands mid season invalidates earlier columns.
Plant material varies with weather, soil and ripeness. Note where it grew and whether it was stored fresh or frozen. The practical detail is set out in Anthotype Process with Spinach Juice Sun-Printed.
Mordants and pH changes alter both color and fade rate. Record every addition, even a pinch.
Reading Anthotype Exposure Times from Your Own Data
If a strip matches your reference patch at three hours and your usual exposure is six, halve the next run and check again.
Doubling and halving around your own recorded times gives you anthotype exposure times you can defend, because you measured them on your own paper.
Keep the same hour of day for every lift. Morning sun and late afternoon sun differ enough to move a result by a whole step.
Score fade in steps rather than adjectives. A scale from zero to five, where five means no visible tone, keeps two people reading the same strip to the same number.
Example: Three Jars on One Windowsill
Example: a maker coats beet, turmeric and marigold emulsions on the same Friday, then exposes one strip of each at the same hour for six days.
Each evening the strips return to the envelope and the log gets one line. By day six the columns disagree, and that disagreement is the finding.
Write the hour, the sky and the strip number. A note you cannot read in six months is a note you never took.
Start the anthotype logbook before the first coat, not after the first failure. Alternative photography at home rarely needs a darkroom; it needs a windowsill, a grey card and a pen. Natural dye sun prints reward the same discipline, because jar color says little about how long a dye holds.
Before coating your own sheet, read the tested beet and turmeric emulsions we already ran, so your columns sit beside a known baseline.
Coating and Cleanup Checklist
- Strain the emulsion through muslin before coating, and label the jar with plant, date and any mordant.
- Keep coated paper in a light tight box, since paper that fogs before exposure is wasted.
- Rinse brushes and trays in a bucket, then dispose of plant pulp and mordant residue under local rules.
Mordants and metal salts are not plant juice, so check disposal guidance for chemical substances before pouring anything down a drain.
Common questions
How long should one test run?
Run until at least one strip reaches your reference patch. Stop early and you learn only that the pigment is slow.
Can I test several pigments on one sheet?
Yes, if every strip gets the same coating and the same position in the frame. Rotate positions between runs so one corner does not always receive less sun.
Do I need to weigh anything?
Record coating passes and jar volume instead of grams. Consistency between your own strips matters more than absolute numbers.
What if every strip fades at the same speed?
Then the reference patch is too dark or the exposure is too long. Tighten the scale and run the test again.
