The first operation to do is to clean the screw. 
The old materials and masterbatches deposits on the screw, generating stripes and black spots.
It does not matter if you are working PE, PP, PC or high temperature materials like PEEK or PSU. We have a purging solution for each case.

The hot runners are very often full of deposits of old plastic and masterbatches. 
It can happen that during the first purging Ultra Plast remove colors which have been processed months before.
Furthermore,by removing old deposits all metal surfaces will be clean and blank.

Yes, you can. We developed the new range QUALIPURGE CS in order to give the best purging results.
All our products are safe for hot runner, as they do not contain any abrasive material.