Heavy discoloration after the freezing step rendering the end product useless

[TheVacuumGuy]

Hi there!

Yesterday i made a -seemingly- nice 3rd batch. However, after the freezer step, the mixture is somehow ruined by blue discoloration of a substancial
part.

This problem occured the previous 2 batches as well, but much worse than this attempt, and well i'd thought could be anything, mostly made some mistakes,
and well try better next time.

It's hard to separate it from the "better" part, as the blue is very strong and even a tiny bit making it to the vacuum filtration causes the end product to be ruined in my opinion.
Sure, using lots of acetone can eventually "fix" it, however it also renders the end product to be just a white powder, missing all the usual properties. Perfectly suitable for the trash can.

I'm starting to think it might be due to the freezing step (too cold maybe, -18), but i'd like to hear some expert opinion of what could be the cause here.

Thanks in advance!

Might be useful: i'm using the procedure in DCM as described in one of the sticky threads, but lower volume (for now, luckily).

Some pictures for clarity of what i mean.


After acidifying, just before packing it up and freezing it overnight:

Just after taking it out next day

What i'd hope for:

 

[riderofapocalypse]

too little acid, just add conc hcl to dcm, stir for 20 min and freeze it

 

[TheVacuumGuy]

Thanks. How to use more acid and still keep above ph 4.5 ? Add bicarb?