I think another reason why you may be obtaining films thicker than what you
expect is probably due to the fact that your soft-bake is not long enough
and may be the films are still retaining quite a bit of solvent.

-Ali-

On 12/1/06, Gareth Jenkins  wrote:
>
> I tried a fresh bottle today fully expecting a more normal thickness but
> it actually turned out a bit thicker!
> My coverage wasn't 100% as I rushed the substrate preparation a bit, so
> I'll try again after the weekend..
> In a way it's nice as I do want to do very thick layers in the future
> and this will make it easier but I would like to find out what is
> causing it.
> My cleanroom is not especially cold during the day (I measured 23C) but
> probably gets cold overnight (there is a big single-glazed metal framed
> window in there). Hence the thermal mass of the bottle could mean it is
> significantly colder than ambient. If true, and temperature really does
> have such a big effect then it occurs to me this may be a nice way of
> increasing the thickness range of any particular SU-8 grade - just keep
> it in a fridge (or oven) for a while prior to use.