How to read a reagent colour chart
This version has been translated from Polish and links to the relevant test kits have been added. In a life-threatening situation call 112. This article is informational and serves harm reduction. It does not encourage the use of psychoactive substances and does not replace medical advice.
A colour chart is a comparison tool, not a lookup table. It shows what a known-pure substance did with that reagent under reasonable conditions, and your job is to decide whether what happened in your well is the same reaction, not whether it is the same pixel. People who expect an exact match get stuck; people who read for the reaction and its speed get an answer.
Four things that change the colour you see
Sample size is the biggest one: too much sample saturates the well and everything goes dark, which is the most common reason a result looks wrong. Time matters, because most reactions develop over seconds to minutes and then degrade as the reagent meets air and light, so the reading is the one inside the window in the instructions. Light matters, so judge in daylight against white rather than under a club light. And the carrier matters, because blotter paper, gel tabs, binders and colouring all contribute their own tint.
Read the progression, not the endpoint
Many reactions move through a sequence, and the sequence carries more information than any single frame of it. Marquis with MDMA goes yellow, then purple, then black; with 2C-B it goes yellow, then green, then blue. If you look only at the final colour you lose the part that distinguishes them, so watch the well rather than checking it once, and photograph it as it develops.
Judge the colour where the reagent has the most contact with the sample rather than at the thinning edge, because the edge is always weaker and always misleading.
Marquis instructions · Mecke instructions · Ehrlich instructions
What a chart can never tell you
How much. Colour intensity is not a purity scale, a strong reaction does not mean a strong sample, and a weak one does not mean a weak sample, because concentration, sample size and timing all push intensity around independently of content. Charts also assume a single substance, so a mixture gives you the loudest compound rather than an average, and the answer to both problems is the same: a plate.
What a TLC test does · Full reagent kit · 800+ substances in the app · TLC purity kit, 84,95 EUR
Questions?
My colour does not match the chart exactly.
Read the reaction and its speed rather than matching a shade. That is what the chart is for, and it is how experienced users read one.
The whole well went black.
Usually too much sample. Use a scraping, and read the edge of the reaction rather than the middle.
Does a stronger colour mean stronger drugs?
No. Intensity is not a purity measure, and no chart can be read as one. Purity needs a TLC plate against a calibrated reference.
How long should I watch?
As long as the instructions for that reagent say, and no longer. Reactions degrade with air and light.
Where can I look up a substance?
The app carries colour results for over 800 substances, offline and without an account.