First, apologies in advance if this question has been asked and answered. I did try searching first, but if so I'd appreciate if someone could point me in the right direction.
I have several old pens with barrels that exhibit discoloration, which I understand to be caused by a chemical reaction between the rubber of the sac and the celluloid of the barrel. It seems that restoring the discolored parts to their original state is not doable -- is it possible instead to cause the cap to discolor? The attached photo shows one example, where the barrel has taken on a lovely color, but is quite different from the cap. I assume that this could perhaps be done over a long time by stuffing a sac in the cap and letting it degrade, but is there a way to hasten the effect?
Thanks kindly for any thoughts,