I usually do simmer rue seeds 3 times, first time with a very little vinegar, then one time in a pressure cooker. This usually produces a compact bed of free base harmalas, which are easy to collect on a filter. I however extract little over 10 grams of FB from 500 grams of rue seends, which seems to low.

This time I pressure cooked the seeds in 3% vinegar, then 3 times simmer, reduced the collected liquid as usual, filitered and based in lye.

This time I got a very thick freebase mush that is hard to impossible to filter, immediately clogs the filters, even cheesecloth is clogged instantly.

The mush settles at 750 ml mark in a 2 000 ml beaker after 2 days of sitting (the photos were taken day before so it's still at 1 000 ml mark), and no more. The free base mush has been washed many times with very slightly basic water.

I tried to re-acidify and filter the liquid, but the acidified tea is even more viscous and hard to filter.

Any ideas what could went wrong and how to remedy the problem?

I was thinking about using strong acid, such as HCl, to possibly break down some residues that might cause the clogging.

The seeds were used whole, ungrounded.

Okay I have mixed in the acid and converted everything to salt form. The tea is very dark showing quite high harmala concentration, much higher than my previous extractions. Pre-soaking the seeds in hot vinegar seems to work very well.

There is a sediment that slowly sinks to the bottom so it seems repeated decanting and diluting the sludge will work, then filter the rest.

I never filter my fb, only ever decant it + do multiple washes.
To increase the efficiency of decanting I transfer them into a tall and narrow container.

I'm not a fan of filtering when the goodies to keep are in the filter and the filtrate is to be discarded, because: A. the amount of the goodies clogs the filter, and B. they're difficult to remove. I prefer to filter when it's the other way around.

With Manske crystals sometimes I combine decanting with filtering, i.e. decant off the liquid 'contaminated' with crystals onto a filter to catch the crystals, while the majority of the crystals stays in the jar as a large 'dough ball', with the help of a spoon to keep it in. The Manske crystals are fluffy enough to not clog the filter.

From 500g seeds I'd expect to get roughly 25g FB. If you get more this time, that will be great news!

I agree filtering is not necessary.

The reason to filter in my case was that I thought something was in the solution even after many washes, that caused the clogging. I then found it was not the case.

I filter the freebase at least in the later stages since it can be thoroughly washed to remove traces of salts and base. Especially the base, since we don't want to smoke sodium hydroxide in any amount.

The vacuum filtration also squeezes water from the acidic mush which may mechanically trap more alkaloids (at least this happens with ayahusca brews, that the bottom of the pot is much stronger than top). The mush can be rinsed with fresh water and squeezed to remove trapped harmalas.

I use thin round paper filter when possible so there is very little material stuck inside the filter. I think simply washing the filter in hot vinegar will release the alkaloids into solution. Of course, some small amount of insolubles are released too, but it does not matter since I will filter the acidic tea anyway.

I also like filtering the acidic harmala tea through a bed of diatomaceous earth. It gives it extra purity.

So far I managed to decant half of the tea, freebase it and remove quite a bit of alkaloids. I topped up the mother liquor with fresh water and waiting for the mush to settle again. It seems this will be long and tedious process.