Photo Resist

[John Stevenson]

The spray stuff in cans.

How can it work, not how does it work.

Can I clean a plate of brass up, spray it with this stuff, let it dry, then burn the etched areas away with a laser the drop it into the ferric chloride ?

I need to get some quite small letters to stand proud of a brass sheet.

Don't mind buying a tin to try it IF it stands a chance of working, alternative is to use a spray can of paint and laser the etched area away.
Anyone done this or seen web sites where it has been done, need to use a laser as all the files are in the laser format.

[awemawson]

John I've used it years ago. It's mainly sensitive to uv light. Make a mask, expose to uv, develop it (developer is usually caustic soda) then rinse in water..etch in ferric chloride. You can get positive and negative working spray.

I found getting an even spray coat a pain and went over to precoated fiberglass copper clad..still got the uv exposure box and a small 'lab line' series of bubble agitated tanks.

[John Stevenson]

Want to miss the developer stage out if I can as the files are already in the laser, might try paint first as I have it.

BTW sent you an email tonight over LED lights.

[RobWilson]

Just use spray paint John . I did mention it earlier 

     

Rob 

[awemawson]

Now you've done it Rob - I really want one of those laser engravers 

John remind me of the details of the one you got. 

[PekkaNF]

I have used Positiv 20 spray. It sor of works, but you have to be compulsive neurotic about the process.

http://www.instructables.com/id/Fantastic-Double-Sided-PCBs-at-home-using-photores/step2/Positiv-20-Spray-application/

Firts you need dust free envitonment. A spec of dust and you have a pinhole.

Then you need to get pretty consistent with spraying...you want even coverage and need to see the wet thickness....sort of right even sheen and it's fine. Edges needs extra attention.

Then you need to "owen" it. I think it was 60 decrees C for 7 minutes or so. I made an owen out of cardboard box.

It sort of works, but it is fiddly and there is a learning curve.

Pekka

[DavidA]

If using caustic soda,  make it a very weak dilution. About a teaspoon to a litre of water.

Dave.

[John Stevenson]

OK paint it is but the salt bath won't work with brass though will it ?
Think I need a trip to Maplins for some Ferric chloride

Andrew,
Mine is one of these.

http://www.ebay.co.uk/itm/50W-CO2-LASER-ENGRAVING-U-FLASH-DISK-AIR-ASSIST-ENGRAVER-CUTTER-HIGH-LEVEL-/271603539253

Been an absolute cracking tool, can't rate it highly enough.

DO NOT even look at the A4 40W versions, they are absolute crap. The one above is a tad over A3

[awemawson]

It must be good - it comes with a free set of allen keys 

What sort of tube life is reasonable to expect do you think?

[John Stevenson]

They reckon about 1,000 hours.
One problem is tubes deteriorate with age as well as use so hard to put a true figure on it and no good buying a spare that that will deteriorate.
News tubes are about £250 and available in a few days