Homebrew PCBs

KPR is currently available. It is sold by Transene Company : 
http://transene.com/pkp/

This place also has materials and supplies: http://www.camconchemical.com/

It is not clear that KPR can be purchased in hobbyist quantities. The 
material has a shelf life, so it is impractical to to buy much more than 
you can use over a few months.

On the subject of the "Blue Paint" from e-bay: I too am confused by the 
presentation on the website. It says to dilute the material with an 
unidentified diluent. They don't seem to offer that material for sale, 
not do they tell us what it is. They do mention that a possible 
substitute is banana oil. I don't know about any of the other members of 
this forum, but I don't keep banana oil in stock because I have never 
encountered  a squeaky banana. Has anyone figured out what the solvent is?

With regard a spinner for applying photoresist, this website has some 
info on building and using your own spinner. Much of the other material 
on the site, although interesting, is not new, and some is out of date: 
http://www.tayloredge.com/reference/Electronics/PWB/pcb.html

Harvey


On 3/2/2017 8:24 AM, wa4qal@... [Homebrew_PCBs] wrote:
>
> Yes and no, with regards to using a UV resin for a photoresist.  The 
> original popular photoresist was KPR (Kodak PhotoResist):
>
> https://en.wikipedia.org/wiki/KPR
>
> That photoresist is UV sensitive, and will harden when exposed to UV 
> light.  Then, it is developed with KPR-developer, a rather nasty mix 
> of volatile and toxic materials (Xylene?) (although I think I remember 
> that safer, alternative developers were available at one point).
>
> The largest problem with KPR is that it is a "negative type" 
> photoresist, in that you need to UV expose the areas which are going 
> to leave Copper.  The world has been searching for an effective 
> "positive type" photoresist for decades.
>
> Now, I haven't tried to obtain any KPR for about 35 years.  I know 
> that, at least at one time, it became quite difficult to obtain.   I'm 
> not sure of the availability now, though.
>
> Dave
>
>