The discussion centers on the phenomenon of enhanced water absorption in clay when placed in a sealed plastic bag submerged in a 5-gallon bucket of water, referred to as scenario D. Participants concluded that the increased pressure from the surrounding water in the bucket, combined with the sealed environment of the bag, facilitates more effective water infiltration into the clay compared to scenarios B and C, where the clay is either submerged directly in water or in a bag without external pressure. The role of density differences and potential chemical interactions, such as pH changes, were also highlighted as factors influencing the absorption process.
PREREQUISITESThis discussion is beneficial for potters, materials scientists, and anyone interested in the hydration processes of clay, as well as those exploring the effects of pressure and chemical interactions on water absorption in porous materials.
Why? The bag foil prevents/hinders transport.ImaginaryTango said:...when you say the bag prevents or slows some kind of exchange - but wouldn't it be that it allows or speeds up an exchange, not slowing it down?
Okay - just trying to straighten it out in my brain.A.T. said:Why? The bag foil prevents/hinders transport.
This sounds like the most likely hypothesis.jbriggs444 said:What about the possibility that capillary action is responsible?
By itself, capillary action will tend to draw water into the clay. This will tend to expel any entrained air. If the clay is entirely immersed, there is nowhere for the entrained air to go. It is trapped and will be under some pressure. At best, it can attempt to bubble out the top. But surface tension will resist bubble formation. If, on the other hand, the clay has a surface exposed to air, then the entrained air has an exit pathway. Capillary action can then fully displace the entrained air.
The plastic bag is helpful because it ensures that air inside the bag will reach 100% relative humidity. The exposed clay will not dry out.
I'm really glad you posted this and shared the quote from @jbriggs444. I did read his post, but maybe, since I was reading a lot of posts, I missed some details and that may be the answer (or the best one we can get without a lot of experiments).Dale said:This sounds like the most likely hypothesis.
It could be tested by comparing a bag with trapped air and a bag with all air removed. It would also be interesting if the bag without air got an air bubble from the air originally inside the clay.