Blocking a tapestry

Last year we had to design our own tapestry and hand it in as the final piece in our first year class.  I posted about it at the time but it wasn't obvious that it had a major problem, it was more a trapezoid than a rectangle.  I didn't know what to do about it, so just handed it in as it was.

You can see the top sides pulling in.

This year, in another class, not tapestry, we learnt how to block embroidery and tapestry (and knitting, I think, although there were no examples tried).  So I got out the work from last year to experiment on.
I had to measure it carefully and decide the dimensions I wanted it to be.  The vertical dimension was easy as there was very little difference across the whole piece.  But the horizontal measurements were 2 cm different at the top and bottom, 27cm and 25cm.  I decided to split the difference and try to make it 26cm wide.
I measured out the space and then pinned the tapestry to the size I wanted.

Pins can be used to keep slits from widening.

Then I steamed it with the industrial steam irons we have on campus.  It was amazing to see the bubbly bits shrink and the tight bits stretch.

It has to be let dry for 24 hours, so I won't see it for a day or so as it has been put away to dry. Here's hoping it stays in proportion when I take out the pins.