The NMP may have softened latent semi-dried ink into a skin? I've put several gallons of NMP through Toshiba CA4s. My usual method was to pull the top ink inlet and syringe the ink through the head. Have you done this?
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artbot
artbot
You'd have to do an acetone ink test by placing acetone on a cured print from your machine AND doing a blend test wherein you mix acetone with uncured ink and let it set overnight to observer its behavior. The blend passes if the ink shows no sign of sediment or coagulation.
H
humen2
Thanks man for the answers 
For the NMP, at first only the magenta was clogged, I've tried syringe flash the head with it, it opened it a bit but not fully (look like a big chunk is stuck in the head). To my stupidity, I've swabbed with NMP the other heads from the outside and It's clogged all the heads.
For the NMP, at first only the magenta was clogged, I've tried syringe flash the head with it, it opened it a bit but not fully (look like a big chunk is stuck in the head). To my stupidity, I've swabbed with NMP the other heads from the outside and It's clogged all the heads
.