Once the pot is fired, there's no more slip or slurry to dissolve into the tea, so I'm puzzLed by what you mean by "chalky" here. Can you explain a little further about what that means?
Well, one thing, I think a lot of slip cast pots tend to be under fired and just because something is fired, even high fired, does not mean there is nothing to flake off into the tea –think Terra-cotta pots. Regardless, I taste this.
Terra-cotta is a low fired product while the Yixing pieces are high fired. Different beasts. Every clay surface and every glaze surface (of all types of glass and ceramic wares) will tend to be affecting the water ("the universal solvent") ............... the question is how much over what period of time and if a change of a particular magnitude can actually be perceived by the taste buds.
To make a clay body for slip casting, particle distribution and suspension capability has to be considered. You typically cannot take a clay body that is formulated for forming processes like handbuilding or throwing characteristics and then just "make" it a slip casting body. Typically the composition of the slipcasting body gets modified to make it work for THAT particular forming method.
And to make a casting body slip, it MUST be deflocculated.... which means that a chemical that affects the ionic properties of the water is added so that it takes less water to make the suspension "fluid". This keeps the pieces from cracking in the molds as they dry due to excess shrinkage. It also decreases the water the mold needs to absorb to get the correct thickness of clay deposit. Slipcasting is a complicated process..... particularly at the commercial level.
I strongly doubt if a straight zisha clay that is used for hand construction would be used for the slipcasting body unaltered.
As to mold lines, there is also the forming process called press moulding. You take a plastic clay body and force it into a mould and then connect the various parts of the mold together to form the final object. This can be done by hand, or by hydraulic pressing methods. So mould lines do not necessarily mean slip casting.
I was told while in Yixing that the nature of the genesis of the pieces is directly related to the pricing, with a further link to the fame of the artist. It was CLEAR that the prices for the better works made out of the "real deal" clay are generally VERY high.
That old saying "you get what you pay for" holds true here. Just sayin'.