JH Enström techiques

Im wondering if anyone here is familiar with the technique used by JH Engström (and other photographers too) to reach these kinds of results.

http://jhengstrom.com/ttd10.html

http://jhengstrom.com/ttd15.html

http://jhengstrom.com/cdg28.html

Would the techniques be used during processing, or printing? I cant really think of a way to reach these kinds of results just using a normal camera and normal processing. Its been on my mind for some time now..

Those almost look like Polaroid Integral film shots. Like SX-70 images.

They remind me of the old Autochorme pictures that you sometimes see. There were some people trying to revive that process recently, but I don't remember who or whether they had any results. Basically, it's a black and white process with a random color dot screen.