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Subject: Re: [Homebrew_PCBs] Re: Out-of-date pre-coated boards

From: Matthew Smith <matt@...>
Date: 2008-06-06

Quoth Andrew at 2008-06-06 08:46...

> Matthew - it is kinsten stuff I had that I
> found to have lost a lot of sensitivity and
> a little bit of contrast when many year out
> of date.
>
> However sometimes when I order the Kinsten
> boards from Perth they come in different
> shades depending on batch. They range from
> drab green to bright green. So there may
> even be marked difference in the "past used
> by" performance in the one brand.

Thanks Andrew. The moral of this story is, therefore, to run a test
strip on every batch of stock. Have a small strip of board and a film
of parallel lines. Partially cover the strip, expose for a minimum
length of time. Uncover a bit more strip, expose for a little longer.
Rinse, then repeat. Develop - and possibly even etch - the strip and
see which exposure time worked best. I think that the term is 'bracketing'.

Cheers

M


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Matthew Smith
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