15 mils is easy. 10 mils with some care. Below that, no promises.

I believe it'll take a 10mil track to go between 63mil pads of a dip
pkg, so it'll be close.

I use the glossy photo basic paper from Staples, or Costco, or Sam's Club,
or whatever branded private label -- it works better than the "premium"
variety photo paper for whatever reason. It all seems to work the same.
The trick is to use copper-brite scouring powder made specifically for
copper and brass along with one of those green dish scouring pads to clean
and microscratch the bejabbers out of the board before applying the resist.
It also helps to preheat the board for about 5 minutes at 150F in a toaster
oven after cleaning but before ironing on the resist.

I better go find me some copper-brite. I've been using comet.


I've used ferric chloride, ammonium persulfate, and muriatic acid - hydrogen
peroxide and I MUCH prefer the muriatic-peroxide combination. What I have
NOT perfected in the etch process yet is a method of agitation for the
etchant. Right now I'm using an aquarium with an air pump and a "bubbling
stone", but would love to find another method. Perhaps I'll work on a
magnet with shrink sleeving and RTV to seal the ends and another magnet on a
motor underneath the aquarium bottom. That seems like a lot of hassle for a
simple agitation, but I haven't found a better way.

Yeah, the persulfate is way too slow without a catalyst even when
heated and agitated, and ferric chloride is just too messy.

Is it really necessary to mix up the peroxide/acid for each session?
Could it be poured back into an airtight dark jug?

I too thought about the magnet stirrer. I just wonder if the magnets
would really setup any circulation in the tank.

The school I teach for has a half dozen good PCB drills, so I'm not yet
forced into that corner. I've also got a BIG pcb shop down the hill a bit,
and they throw away carbide drills by the sackful. I've gotten them to
throw a few sacks my way.

No such luck in my garage.

Jim