OTE Stain (Oolong Tea Extract) – Powder


Non-toxic contrast agent
High purity (food-grade quality)
For positive contrast
Packaging: 10g

SKU: GP18-10 Category:


Our Oolong tea extract contains a high level of tannin and ensuring high purity. OTE (Oolong Tea Extract) functions based on its tannin content for maximum efficiency during contrasts.

Preparation of OTE Solution and Use of OTE Powder:The preparation of the OTE solution is similar to steeping tea in 70°C water, no more.

Using a magnetic stirrer set at 70°C, dissolve your OTE powder at a concentration of 0.2% (as saturation is reached at 0.3%).
After complete dissolution (achieved within 15 to 30 minutes under agitation at 70°C),
Filter your OTE extract solution at 0.45µ or preferably at 0.22µ.
Store it in a small Eppendorf tube filled to the maximum to reduce oxygen-containing air, or in an AirLess Black bottle, and keep it in the refrigerator.
Store in darkness at 4°C (when handling, always let your solutions return to room temperature).
Contrast your grids with OTE for 15 to 20 minutes, in darkness, at room temperature.
Simply drain, no rinsing or very short washing for 1 to 2 seconds, after drying.
Post-stain for 1 to 2 minutes with lead citrate according to Reynolds (Ref # 11300).
Drain, rinse briefly, dry, and ready to observe.
EM_Grade Data Sheet:

This prepared aqueous OTE solution is slightly acidic, with a pH of 6 (you can replace the water with a phosphate or cacodylate Na buffer to adjust your pH).

You can find the protocol for preparing your OTE solution (see or download the technical note below).

Technical note the oolong powder

EM-gradetechnical note the oolong powder

No MSDS (Material Safety Data Sheet) as OTE is a food product

Additional information