Did you adequately clean the pcbs before applying your resist?
Usually i find blank pcbs have some sort of coating or treatment to prevent oxidation, of course this should be removed by the usual cleaning process before imaging. If you didn't, I could imagine that sort of long etch problem.
Also, heat should not be necessary, with hcl + h202
On Nov 23, 2016 07:57, "kbyrne10@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:
. It also took 15 to 20 min to etch boards at 120 degree temps.