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Subject: Re: [Homebrew_PCBs] Length of sunlight exposure of photosensitive boards

From: Leon Heller <leon355@...>
Date: 2011-05-08

On 08/05/2011 12:55, DJ Delorie wrote:
>
> James English<jimenglish123@...> writes:
>> Does anyone out there have experience with exposing a photosensitive
>> board through a negative to sunlight?
>
> Sunlight is very variable, but in general, anyone doing UV exposure
> should have a "transmission step wedge" - this is a plastic film with
> various calibrated shades of grey printed on it. Using this, you can
> calibrate ∗any∗ UV source and, with a little math, figure out the ideal
> exposure time in one trial run.

I found the optimum exposure for my process by sliding a piece of
cardboard across a test piece of laminate with a test piece of artwork,
moving it at 1 minute intervals.

Leon
--
Leon Heller
G1HSM