Here's what works for me, I use a HP 7475 pen plotter with a slot cut in the
case. I use a GC #22-222 Etch Resist Ink Pen. 1/64 " tip. Its fitted into a
drilled and honed out dried up HP pen. I have to keep etching fast. I heat Fe
CL3 on my grill outside, in a oven dish. Wear glasses, gloves, and apron. I
use a oven baster to spray the center of the project. The edges seem to eat
off first and I keep the acid going to the board center. This is not a time to
walk off and come back. I keep an eye on the board till it is complete. You
can always put it back in, but once its eaten the copper away its done.
Stefan Trethan wrote:
> @Dave
> thanks for the tip with laquer thinner for solving colophony resin.
> i tried it and it is much better than alcohol.
> The "laquer" is the same density / concentration in the whole jar, it stays
> good dissolved without stirring etc.
> with alcohol it was always thicker at the bottom (with acetone too).
> Dries quick and leaves a shiny coat.
>
> I actually tried it as a resin for etching (because the quality is much
> better now).
> The problem is the plotter pens i have (carbide tipped) don't leave a thick
> enough layer to resist HCl H2O2.
> I will try repeated plotting and maybe try Fe3Cl which i have standing
> around somewhere (Does it decay in a sealed Bottle?).
>
> But i applied it with a piece of wire and with a piece of a paper towel
> "disposeable brush with needle-nose pliers handle).
>
> And this areas resisted the etching very well.
> So i think the plotter pens simply make a too thin layer.
>
> any ideas? - would be great to solder the boards with resin layer and also
> protection against corrosion.
>
> st
>
>
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