Stained vegetal resin converter tube from a FPR Himalaya

After holding Diamine (Inkvent Red Edition) Winter Spice for eight weeks, this converter with a smelly vegetal resin tube has acquired a permanent blush. Soaking in dilute ammonia solution, and scrubbing (using a cotton tip amply soaked) with Herbin fountain pen cleaning solution, does not remedy the condition beyond what you can see here.

So, you may want to leave a piece of clear plastic that is similar to the barrel material, to bath for a few weeks in that ink in a test tube or sample vial, as a test before filling your precious, large ink capacity, barrel-cavity-as-ink-reservoir demonstrator pen with it. After all, the idea of using such a pen would be to leave a lot of ink in it so that it would be ready to write for a prolonged period, no?