There are concerns over Picric in the fly fishing industry. The Semperfli Picric Acid Dye is laboratory manufactured for us specially and is safe for dying of fly tying feathers, furs and synthetics. We use Picric diluted 100ml. This is ideal to obtain a variety of olive shades in natural fly tying materials, both fur and feathers.
Picric crystals were dangerous and used for explosives, indeed the navy used this to fire canons pre 1916. It was first mentioned in alchemical writings by Johann Rudolf Glauber in 1742. The picric would form very sensitive picric salts within days of filling the shells and would often detonate from the shock of firing. Lacquering the insides of the shells and spraying them with a turpentine starch solution neutralised the picric acid and prevented it from forming picric salts. Today we use diluted picric and store this in plastic containers. We do not use metals even for agitation and it is perfectly safe.
We suggest to use plastic bowls for dilution and use plastic tools to agitate the picric acid. We leave the materials in until they have visibly changed. Some materials like thick wings, grouse for example may take a couple of days for full penetration of the picric acid whereas pheasant tails can dye in 15 minutes to 1 hour. We use latex gloves as picric, although not dangerous does make your hand look like you have smoked 60 cigarettes per day for years we have found from accidental spillage when we first started working with the laboratory to manufacture the product. For safety with all dying, from picric dying to dying we use safety glasses and latex gloves.
Once the materials have achieved the olive color that you require simply wash off excess picric under running water. We then dry the feathers and furs with a drying cabinet or in alternative with a hairdryer. For hands protection use protective gloves. The most suitable glove should be chosen in consultation with the gloves supplier, who can inform about the breakthrough time of the glove material. For eye protection wear approved, tight-fitting safety glasses where splashing is probable. Work in airy environments to protect breathing apparatus.