Model Forum / General / Models / December 2005

I bought one of those Micro Mark photo etch kits a couple of months ago.
 The procedure sounded quite daunting, and a slip accompanying it
warned of wasting a bit of the materials in the first few attempts as
you acquire the skill. So I took it super cautious, real step-by-step.

Yesterday I finished my first sheet of photo etched parts.  These were
friction shock absorber blades for my scratch 1/8 scale locomobile
racer.  The blades are not super small, so I thought they'd be a good
starting project.  I did include some spring star washers that are
needed for the shocks also- these are a bit smaller and finer in detail.

I needed 8 blades and two washers.  I laid out 12 blades for the blank
and five washers.  I ended up with all twelve blades usable, but some
have some blemishes.  I will have no problem selecting the eight best.
One of the washers was a bit crudey, but since I only needed two I am
delighted.

I did modify one task compared to what the fine, lengthy instruction
book says.  You are supposed to strip the photo resist off the etched
parts with concentrated lye.  They include latex gloves for this step
(and for the etching in ferric cloride).  I didn't like the idea of
working with small parts in concentrated lye, and suspected acetone
would also strip off the photoresist.  I was right- I put the sheet in
one of the trays they provide and poured in enough (about a quarter
inch) of acetone, and indeed it stripped the resist off fine.

The worst part of the whole project was etching evenly in the ferric
cloride bath.  They provide an aerator, but that was not quite enough. I
still had the resist starting to disappear at one end of the sheet
before the other end ate through the etching areas.  But the difference
was not bad-, I was able to flex the sheet in the area that was not
etched all the way through, to seperate the parts from the sheet.

All in all I was delighted with the results. I will now do a few finer
detail parts and get on with the project.