How to use a reagent test kit properly

A reagent test takes 30 seconds, costs a few cents per use, and is the single most effective harm-reduction step you can take with a pressed or unknown substance. It is also routinely misused. This guide covers the practical details that get glossed over in the kits' instructions.

What a reagent kit actually does

Reagent kits are presumptive colorimetric tests. You drop a small amount of acid onto a tiny scraping of your sample and watch the color change over 30–60 seconds. Each reagent gives a known reaction with known compounds. The kit confirms presence; it does not confirm purity, dose, or absence of adulterants.

A positive reagent reaction tells you a substance class is present. It does not tell you how much, or what else might also be present. This is why we recommend multi-reagent testing. Different reagents react differently with different compounds, and overlapping results let you triangulate.

What you need

• The reagent itself, refrigerated, in its original bottle
• A small ceramic or glass plate (or the cap of the bottle)
• A toothpick or razor blade for scraping a tiny sample
• Good lighting, ideally daylight
• A reference color chart for the specific reagent and substance class
• A phone timer

Step by step

1. Take a tiny sample. A grain of rice's worth of powder, a corner of a pill, or 1 mm of a blotter. More sample does not give a clearer result; it usually gives a less clear one.
2. Place the sample on a non-reactive surface. White ceramic shows colors most accurately. Avoid plastic, some reagents will react with it.
3. Drop the reagent on top. Just one drop. The bottle should hover; do not touch the sample.
4. Watch the color develop over 60 seconds. The reaction is often fastest in the first 5 seconds, then evolves. Note the peak color, not the final color.
5. Compare to the reference chart for that specific reagent. Reactions vary substantially between reagents. Marquis purple is not the same purple as Ehrlich purple.
6. Repeat with a second reagent to confirm. If you only have Marquis, you cannot distinguish MDMA from PMA or PMMA. And PMA has killed people at MDMA-typical doses.

Common pitfalls

• Using only Marquis. Marquis turns purple-black for MDMA, but it also turns purple-black for PMA, PMMA, methylone, MDA and several others. Always confirm with Mandelin and Mecke, or Simon's (for secondary amines).
• Misreading the color. Reagent colors evolve. The five-second color is not the final color. The peak color is the diagnostic one.
• Bad lighting. Yellow indoor light shifts blues and greens noticeably. Use a window if you can.
• Old reagent. Reagents degrade. A bottle older than 12 months, or one stored at room temperature for any length of time, may give weak or shifted reactions. Keep them in the fridge.
• Cross-contamination. A previously used toothpick will throw off the next test. Use a fresh one each time.

Reagent recommendations by substance class

When reagent testing isn't enough

For pure compounds and unknown solids, fentanyl test strips are a separate and necessary test, especially in regions where unintentional fentanyl contamination is a known risk. Reagent kits do not detect fentanyl.

For final certainty, send a sample to a drug-checking service if one is available in your region (DanceSafe in the US, MAPS-affiliated programs in some EU countries, the Spanish Energy Control project, or organizations operating under PsyCare-style permissions at festivals).