OK, I think I am coming up to a reality check. Severe erosion occurs around a tiny pinhole just like around a very thin line.  Not only does etching take place put it blooms under the resist and starts to lift the resist and the problem becomes run-a-way.  The thinnest line in this piece was at the top of the fork like figure.  All the lines elsewhere remain sharp and acceptable.

 

The blooms to the left of the figure are pinholes that have bloomed to potholes.

 

Now for something interesting.  If the line in the resist (ground) is narrow, then the problem occurs. If the same narrow line is created as a negative image, then the problem does not occur.  It seems that a “hot spot” is created at a pin hole (or a line of pinholes) but does not ever occur at the interface of a large “bitten” area and its boundary.

 

OK, I can examine a plate for pin holes and plug ‘em  but I guess I have to be sure that I have no lines that are pin hole size in width.  The critical dimension appears to be any opening in the resist that is .01 inch or lower.  If the design has a spot this size then blooming is going to happen with my set-up.

 

So, I am going to try and lower that voltage even more to see what effect that has or maybe try a different resist film.  Until I figure that out, I have to stay away from thin lines and work with designs having coarse open areas.

 

Oh, I almost forgot.  I let plate with Puretch sit in the copper sulphate etch solution bath with no current for 2.5 hours and there was no deterioration of the film.

 

Need some help here, folks! =)