Diazo Emulsion

[Prosperi-Tees]

Can you use diazo emulsion without adding the diazo? Why or why not?

[Frog]

No. Without the Diazo, it has no reactivity with light. It's just essentially block-out.
Used to make our own at one shop with white glue, coloring, and I think sodium bichromate to make it photographically sensitive.

[merchmonster]

I had a guy who threw away the diazo and coated screens with unsensitized emulsion. That was fun times troubleshooting

[Prosperi-Tees]

Ok thanks. I was curious if the diazo was just for water resistance. I've been using sp1400 and while I love the price, the reclaiming is a bit tougher. Still have a couple gallons to go thru before thinking about changing to a one part with easier reclaim. Any suggestions on an inexpensive one part emulsion? Might be hard to beat the $30 sp1400 though.

[3Deep]

Can't beat the price of 30 bucks but a really good two part emulsion is Imagemate DC-521 44.95 a gal from Valleylitho.com which is now called Superior Screen Printing Supplies.  Homer turned me on to HXT works with water base or DC inks I can't tell you the price I just order it might need to see what I'm paying LOL.

[Prosperi-Tees]

I tried a 2 part from Xenon that reclaimed like a dream but was pinhole city so that one is out. I dont need water resistance. I am thinking of trying Ulano Orange again. It is about $45 a gal. I figure I could cut my exposure times in half and save a minute or so per screen and then I will be ahead of the game.

[Frog]

I tried a 2 part from Xenon that reclaimed like a dream but was pinhole city so that one is out. I dont need water resistance. I am thinking of trying Ulano Orange again. It is about $45 a gal. I figure I could cut my exposure times in half and save a minute or so per screen and then I will be ahead of the game.

Pinholes are unlikely to be caused by a specific emulsion, but rather are a product of less-than-stellar housekeeping. Perhaps, though, some are more forgiving than others.

[Prosperi-Tees]

Maybe so, but I experience zero pinholes on the SP1400, I can't remember having one for a couple years at least, once I switched over to the Xenon, pinholes. Can pinholes be caused by overexposure?

[abchung]

For me. Pin holes are caused by good emulsion that can expose fine details. We need to wipe down our glass before exposure.
Spot colour:  local emulsion, $5/kg
Halftone: imported $20/kg

Sent from my SM-G930F using Tapatalk

[noortrd]

whats the differnce between diazo and presensitize emulsion? in presensitize they add diazo before?.

[Frog]

Maybe so, but I experience zero pinholes on the SP1400, I can't remember having one for a couple years at least, once I switched over to the Xenon, pinholes. Can pinholes be caused by overexposure?

Pinholes are typically specks of dust which either break through during a run, or during developing. Overexposure would tend to make them bust through less due to stronger emulsion.

[Frog]

whats the differnce between diazo and presensitize emulsion? in presensitize they add diazo before?.

Well, they add a sensitizer different than diazo. A photoreactive salt (Styryl Basolium Quaternary), is bonded to the polyvinyl base during the manufacturing process.
It has a much longer shelf life.

[Doug B]

  I know we all want to save a buck or two but to me at least it seems that is one
of the things I don't mind paying for. Good SCREEN printing starts with good SCREENS.
I use the emulsion that works best for me regardless of the cost. I can cut corners in
other less critical areas.

[Prosperi-Tees]

I agree. Thats why I want to shave some exposure time and some reclaim time. Just have to find one that works for me.

[ABuffington]

SP-1400 reclaim issues?  Diazo's are some of the easiest to reclaim.  Try mixing ER-605 from Murakami at 8 parts water to 1 part ER-605.  Are you letting the emulsion remover dry at all on the screen before blasting out?  If so emulsion remover that is left to dry on a screen can make it almost permanent.  the other tip would be to use a dip tank for reclaiming.  PM me for other additives for hardened screens.  Still reclaimable.  Are you reclaiming with a pressure washer as well?  Stronger PSI always helps in reclaiming.  Used to have a 5000 psi pressure washer that could reclaim without emulsion remover! 

Frog:  Glad you are still kicking after using Bichromate sensitizer.  For those that are unaware this is one serious cancer causing sensitizer that should never be used.  There are a few parts of the world who still use it and it can kill all aquatic life in a stream for years for miles downstream. 

Al