Filternatives

I admit, when I ordered his VST Refractometer, Vince from VST labs already suggested I might order extra syringe filters but at the time, 50 of those seemed a lot to get started. Of course I rushed through most of them in the first week so I ordered 50 more. They don't come cheap though: $89 for fifty plus $34 for shipping to NL.

As I ordered 500 pipettes and a box of #7syringes locally from Hinmeijer, I wondered if compatible filters could also be found nearby. René Hinmeijer is looking into this and Adriaan, a fellow roaster from the Dutch forum, quickly found a possible alternative from an Asian company reselling German filters: Minisart by Sartorius. These cost me not much more than the postage of the original VST filters. They are "high flow" syringes with 0.2 micrometer pores. I do not know the pore size of the originals though.

Since the special filters are not necessary when measuring coffee that has passed through paper filters, like drip coffee, I also got a Hario V60 Dripper.

If the measurements of the VST and the German filters come close, the latter would be a great alternative and if a particular measurement is most critical, I could double check the measurement with the original filter, to be sure my readings are compatible with what others would get with the same lab standard.

I took 20g of Finca Tamana beans roasted 17 february (Tonino # 84 today) and pulled 30g espresso. Cooled in a larger ceramic cup, stirred well, filled two identical syringes, screwed a VST on one, a Minisart on the other and pushed a few ml's with each into their own identical shot glass.

Even though the Minisart is a "high flow" filter, it took much longer (and more power) to push enough fluid out of it. Afterwards, on close up pictures of the filter, it showed two cracks. I can understand why the manual advises to "take care when using syringes with a volume less than 10ml since they can generate a pressure greater than the maximum operating pressure of the Minisart unit."

Next I took two brand new pipettes and did my measurements after first calibrating the refractometer and cleaning the eye of the meter with alcohol between measurements.

The Minisart sample showed 11.1 % TDS and the VST sample showed 11.2 % TDS.

So that's very very close and if subsequent comparisons turn out as good, this will be a fine alternative as long as I keep my glasses on and take care not to explode the filters.

The drip alternative (the leftover poured onto a filter which I made wet with tap water first) showed 9.8 % TDS on the first ml's that passed. I should try this again, this time on a dry filter paper and with more espresso, taking the time to let it all drip through.