Vigorous stirring
The procedure for measurements as advised by VST labs is (in my words):
1) allow 1 minute for espresso to cool & CO2 to diffuse out of solution. Stir sample 5-6 seconds
2) with new unused syringe below crema, draw 3-4ml
3) attach filter
4) push 2 ml out into a glass, let cool 30s
5) draw 0.2-0.4ml in new unused pipette
6) transfer to sample well of refractometer
7) allow 20-30s to get temperature equal
8 measure (a few times)
I think the duration of the cooling times are merely indicative, or minimum times because for instance in the illustrations with the advise fairly small cups and glasses are used and I use small but heavy material with more mass on room temp to help cool down the fluids.
In the video by Matt Perger (http://www.youtube.com/watch?v=fL7vNbEcsxk), the stirring is done by vigorously sucking up and pushing out coffee using the syringe and that seems much more effective to me than stirring a few seconds with a spoon or the tip of the syringe.
In the video by Coffee Company of Amsterdam, step 4) is skipped: coffee is drawn into the syringe, the filter is attached and fluid is immediately pushed out onto the refractometer: https://vimeo.com/84681146 (see 2:08)
Yesterday, I tried drawing a large sample and then pushing out three times 2ml into three different glasses. The refractometer showed 14.6%, 14.7% and 14.8% on the three samples (Malabar), so the later bits out of the increasiningly saturated filter showed slightly higher TDS % rates.
On this sample of espresso, I also did the vigorous stirring using the syringe in-out routine mixing the fluid well. I will try this with other measurements as well, to see if this gets me (slightly) different results than just stirring a few seconds with a spoon or spatula.
Today I did the same stirring, with my favorite Panama Los Lajones beans from Graziano Cruz (Tonino # 96):
For the looks, the grind could be a bit finer still to get a little darker leopard-skin crema, but the taste is much to my liking. It reminds me of Indonesian coffee with Ethiopian 'unwashed' elements.
This was done using the Mahlkönig Vario grinder, and the Rocket E61 machine so I will need to do this a few times on the other configuration to see if it's the vigorous stirring that causes the TDS reading being higher or something else.
1) allow 1 minute for espresso to cool & CO2 to diffuse out of solution. Stir sample 5-6 seconds
2) with new unused syringe below crema, draw 3-4ml
3) attach filter
4) push 2 ml out into a glass, let cool 30s
5) draw 0.2-0.4ml in new unused pipette
6) transfer to sample well of refractometer
7) allow 20-30s to get temperature equal
8 measure (a few times)
I think the duration of the cooling times are merely indicative, or minimum times because for instance in the illustrations with the advise fairly small cups and glasses are used and I use small but heavy material with more mass on room temp to help cool down the fluids.
In the video by Matt Perger (http://www.youtube.com/watch?v=fL7vNbEcsxk), the stirring is done by vigorously sucking up and pushing out coffee using the syringe and that seems much more effective to me than stirring a few seconds with a spoon or the tip of the syringe.
In the video by Coffee Company of Amsterdam, step 4) is skipped: coffee is drawn into the syringe, the filter is attached and fluid is immediately pushed out onto the refractometer: https://vimeo.com/84681146 (see 2:08)
Yesterday, I tried drawing a large sample and then pushing out three times 2ml into three different glasses. The refractometer showed 14.6%, 14.7% and 14.8% on the three samples (Malabar), so the later bits out of the increasiningly saturated filter showed slightly higher TDS % rates.
On this sample of espresso, I also did the vigorous stirring using the syringe in-out routine mixing the fluid well. I will try this with other measurements as well, to see if this gets me (slightly) different results than just stirring a few seconds with a spoon or spatula.
Today I did the same stirring, with my favorite Panama Los Lajones beans from Graziano Cruz (Tonino # 96):
This was done using the Mahlkönig Vario grinder, and the Rocket E61 machine so I will need to do this a few times on the other configuration to see if it's the vigorous stirring that causes the TDS reading being higher or something else.
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