Thank you

I send to them, but I don't get a replay

The replacing of markers is preferable, strictly speaking, but in our studies in field of sport biomechanics we try to clean markers by wake solvents with following test. 

Thank you Sir Serge V. Shil’ko

Could you give me some examples for these solvents and the test you do?

For example, you may apply usial washing agents, containing surfactant species with water. Testing after cleaning presumes  visual controlling or the checking of reflectory ability by device (is better). For this aim you may use new marker to compare results. If refractory ability of old marker after cleaning remained much less than etalon, then replacing is necessary).

All the best,

Serge 

Thank you Sir Serge V. Shil’ko