[seszett]

> Wouldn't that just mean you have to wait longer?

You would have to wait much longer with a standard enlarger, probably several days and that's without taking into account reciprocity failure. In practice, it just wouldn't work.

I haven't tried platinotype myself since platinium and paladium are so expensive, but I do print a lot of cyanotype which has a similarly low sensitivity and I built a UV enlarger for that, which works quite well with exposure times on the order of a few minutes for enlarging 35mm onto A5 paper.

It requires a 40W 365nm UV LED source though, cooling for the negative in order not to burn it, and a few other tricks to get it to work well.