Why not just experiment with water until it just 'looks' right. Most spray
etcher are horizontal. Vertical spray etching will have lot more etchant
running down at the bottom of the panel. I don't think you need to worry
about supply of fresh etchant with spraying, the pressure will quickly remove
any reactive products with its force. I wouldn't yet worry about differences
with etching rates on top and bottom. There are probably lot more important
things to consider first, like pump pressure, nozzle shape, nozzle
positioning and filtration. I thought about building my own but it started to
get too complicated and expensive. I think bubble agitation still has a lot
to offer provided you use an adequate air supply. I'm still looking around
for a cheap small regenerative air blower or a large diaphragm pump like
those used in aeration of septic tanks, and large fish ponds. These pumps
sell for $400 to $600 new in Australia. Not a viable option for a hobbyist.
Adam
duncanbourne wrote:
> Hi all,
>
> I'm thinking of making a DIY spray etcher, using sodium persulphate,
> but wondered if you experts could answer some questions for me ;-)
>
> In a professional spray etcher, are the boards horizontal? If so, is
> the etchant sprayed from above or below? I'm worried that a
> vertically hung board will result in uneven etching due to the
> etchant running downwards, and a horizontal board sprayed from above
> will quickly become covered in used etchant, reducing the
> effectiveness of the fresh etchant arriving... Is spraying from
> underneath possible/workable?
>
> Does anyone have experience of professional spray etchers that they
> could share with the group?
>
> TIA
>
> Duncan
>
>
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