The "shrinkage" is compensated for by printing the green parts 20% larger than the final size. The real shrinkage/ distortion problem is due to the fact that during the sintering process glass, unlike metal, becomes a thick viscous liquid.
Molecular attraction will cause all liquid bodies to pull towards the center of it's own mass. To illustrate; If you heat a tiny chip of glass or metal until it melts, it will always form into a nearly perfect sphere. In zero gravity, like on the Space Shuttle, (
go Discovery), a spilled liquid always forms a perfect ball.
So, as a printed glass part begins to fuse and coalesce into a solid mass these forces will come into play. And sometimes in dramatic and unwanted ways. Any angled cross section or cube will shrink asymmetricaly and the result is visually obvious. Faces of a cube will dish in towards the center. A square rod section with become more like a trapezoid. On the other hand, spheres, rounded or curved sections shrink/distort in a more symmetrical manner. Although the same amount of shrinkage is actually occuring, it is just not so noticeable.
Maybe some braniac could create an algorythm to compensate for this phenemona but it's probably simpler to learn and understand how and why materials behave as they do. Then, design good parts within the laws of nature. PUSH THE LIMITS but respect the laws.
-G