No doubt, H2SO4/H2O2 is the best of best to remove
organic spots. The only problem might be that the
solution is hot and soda lime masks do not like fast
expansion/contraction. In other words, after leaving
mask in Piranha for a few minutes, take is out and
leave it to cool down before you immerse it into DI
water, otherwise you risk the mask will crack (own
experience).
If you want to be on a safe side, drop mask into a
cool piranha, warm it up with mask immerse adn after
10 minutes or so at 120 C temperature, take it out,
wait for 2 minutes and only after that dip it into DI.
Good luck. Pavel

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