There are different ways porosity can be measured. The following is from wikipedia:
https://en.m.wikipedia.org/wiki/Porosity
And some methods:Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of void space accessible from the surface (cf. closed-cell foam).
Imbibition methods,[5] i.e., immersion of the porous sample, under vacuum, in a fluid that preferentially wets the pores.Water saturation method (pore volume = total volume of water − volume of water left after soaking).
Water evaporation method (pore volume = (weight of saturated sample − weight of dried sample)/density of water)
The water evaporation method is also described on this pottery page:
https://digitalfire.com/glossary/clay+body+porosity
A few notable items from the pottery page:Porosity is measured by the weight increase when boiled in water.
- X% porosity =X% increase in mass after clay is boiled in water
- An interesting process in which a potter measures the porosity of a clay under a range of different firing conditions in order to determine the firing parameters that minimizes porosity. A curve can be generated, and the page claims that porosity reaches a minimum as temperature increases but then goes back up again as temperature continues to increase.
- Not uncommon for earthen ware to have up to 3% porosity
- The minimum porosity of some clays will remain relatively high irrespective of firing temperature
I propose two approaches based on the evaporation test:
Formal method:
1. Measure dry pot weight
2. Take pot and submerge it in boiling water for X minutes
3. Rinse pot 2x with boiling water
4. Shake pot to get water out of nooks and crannies
5. Wait briefly for pot to appear dry visually or pat dry pot with cloth
6. Measure pot weight at time 0
7. Keep measuring pot weight over time until pot reaches dry weight
8. Plot curve of change in pot weight over time
Real-use method:
1. Measure dry pot weight
2. Have a typical session with pot
3. Rinse pot 2x with boiling water
4. Shake pot to get water out of nooks and crannies
5. Wait briefly for pot to appear dry visually or pat dry pot with cloth
6. Measure pot weight at time 0
7. Keep measuring pot weight over time until pot reaches dry weight
8. Plot curve of change in pot weight over time
The formal method will be more objective but the conditions may not be reflective of real life brewing conditions. On the other hand, the real use method introduces a lot of variability and may not translate from person to person.
However, I believe by drawing an evaporation curve, the overall shape of the curve and the rate of drying should be mostly consistent between methods.