Blacklights vs flouro's in exposure unit.

[Frog]

You are obviously not doing big runs so why have thicker emulsion.
Coat 1:1 on the thin edge.
The thinner coating will be easier to expose.

Maxie, respectfully, I have to point out that a properly made screen is too important a component of the screen printing process, and faster exposure is not enough to sacrifice coating a screen for maximum effect.

[Wildcard]

I didn't make the unit, but I'll open it up and look into raising the lamps closer to the glass.
My runs aren't large, but I keep some screens for my in house product range that will do thousands of impressions over a year. Although mostly my thicker stencils are for short run white on black prints, or printing to poly mesh polos etc.
I guess getting back to the initial question, I really want to understand why the change from a regular fluoro setup to expensive uv lamps didn't improve exposure time dramatically.


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[abchung]

Don't just get any UV lamps. I got UV lamps that sterilise tools for doctors or dentist. that did not help. You just have to get the ones that gives out the right frequency. Money down the drain. So I got a Metal Halide lamp (15000Kelvin)

Check your glass. Look at the edge, is it tinted green? I think green means there is UV protection. That means you have to change your glass or change to a film system.
FILM SYSTEM.
I use plywood instead of a sheet of glass. I cut a rectangular hole big enough so the wood is still supporting the frame.
I then cover the whole wooden board with a thin film of plastic. If you just cover the hole, there will be air leaking through the board, which will reduce the vacuum pressure.
The film system gave me better Emulsion over Mesh thickness. My print of white is more opaque.

I used black lights for years, with a vacuum table.
Exposure time about 6 min and always had some slime inside the screen.
Just bought a 300 W LED from Saati.
Best thing I could have done, with Diazo 4.5 min exposure and with photopolymer (PHU) 45sec.
Great detail and no slime.

Maxie, can you tell me which Saati website you got your Lamp? Thanks

[Frog]

Check your glass. Look at the edge, is it tinted green? I think green means there is UV protection. That means you have to change your glass or change to a film system.
FILM SYSTEM.
I use plywood instead of a sheet of glass. I cut a rectangular hole big enough so the wood is still supporting the frame.
I then cover the whole wooden board with a thin film of plastic. If you just cover the hole, there will be air leaking through the board, which will reduce the vacuum pressure.
The film system gave me better Emulsion over Mesh thickness. My print of white is more opaque.

Why better EOM? Because less emulsion is underexposed and rinsing away?

Your film method brings to mind this tried and true ready-to-go DIY method. Just add sun to go completely "commando"

[Maxie]

-how thick are you coating and on what mesh counts?
>Coating 2+1 (sub side then ink side) and this particular test was on 55T (metric) mesh

Frog I don't think you are compromising coating 1:1 on a 55 mesh (about 125).   For ten years I have been running a automatic with fluorescent black lamps so exposure should be fine.

The 300 W LED is available from Saati USA, contact Greg at gjensen@saati.com

[Frog]

Most of us over here have gradually changed to much higher mesh counts than we used to use.
Whites and other opaques used to typically go on 110's, now are usually on 160's (or higher)
125's in my shop are reserved for runs on fleece.

When using the "Glisten Method" described in the linked article, it really doesn't matter which edge or how many times you stroke. It's kind of like light units rather than time when exposing. It visually indicates quantity of emulsion over mesh. That's the simple beauty of it.

[Shanarchy]

If your film is not opaque enough (hold it up to a light and is it black?) You can print two and double them up. I'm wondering if you need to underexpose due to a weak film? That would cause the slime of an underexposed screen. Then get an Epson 1430 and real films from a supplier. This stuff is cheap and works great. http://store.techsupportsps.com/products/acorn-inkjet-wp-film

Switch you bulbs out for grow light bulbs from Home Depot/Lowes. They provide better UV. Or better yet order the right bulbs from a light supply store (http://www.genesislamp.com/f30t8350bl.html).

Bulbs should be about 5" apart and about 2" top of the bulb to the glass. (I'm looking at my old NuArc florescent backup unit). 5 bulbs would be perfect. If your unit isn't up to these specs build a new one. It's cheap and quick to do. While you're at it put the books back on the shelf, and get a couple of hinges and build a compression lid as Frog indicated.

I'm guessing the above two reasons are why your exposure is taking so long.

Ulano orange is very user friendly. Should expose in 2-3 minutes on a proper florescent unit.

And get an exposure calculator and properly dial in the exposure time.

[abchung]

Why better EOM? Because less emulsion is underexposed and rinsing away?

Same method of coating(2/2). Same time. Same emulsions.
Less emulsion rinsing away (less or no slime).

My workers think no need for print-flash-print anymore.....But I still want it to be whiter.

I also noticed I am getting better edges. (Note: I was using the "Normal" glass before the film).

The 300 W LED is available from Saati USA, contact Greg at gjensen@saati.com

Thanks for the info.

[Wildcard]

So I've got a sample of low iron super clear glass and ran a step test with half the screen on the old glass and half on the clear glass strip. Again, I was disappointed that it made no difference, so I'm not going to spend $100 on a new glass top.
I have some Ulano Orange on the way and hope to test this week. Otherwise it seems my last fix option is to reduce distance from lamp to glass. I opened the box up and it won't be easy to change with how it's rigged up, but I'll figure it out.
I'm sure this issue is behind my problems with trying to print a smooth white on black.


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[Shanarchy]

So I've got a sample of low iron super clear glass and ran a step test with half the screen on the old glass and half on the clear glass strip. Again, I was disappointed that it made no difference, so I'm not going to spend $100 on a new glass top.
I have some Ulano Orange on the way and hope to test this week. Otherwise it seems my last fix option is to reduce distance from lamp to glass. I opened the box up and it won't be easy to change with how it's rigged up, but I'll figure it out.
I'm sure this issue is behind my problems with trying to print a smooth white on black.


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Build a new one. Go to Home Depot/ Lowes lumber yard and and have wood cut to the right size. A few screws. You can probably re-use the light fixtures in your old unit. Order the right lights as I posted above.

Stir your ink (use a drill if need be) until it's easy to stir.

Flood.
Print.
HARD DRY STROKE.
Flash.
Flood.
Print.

A 100% cotton will help as well. Miami ink Superior is real nice. QCM XOLB is a very nice manual friendly low bleed white. There's a bunch of other good ones.

[Frog]

While he may have his "down under" equivalent of Home Depot for building stuff, some ink and other supply recommendations may be difficult to obtain in Wildcard's location, Australia

[Shanarchy]

While he may have his "down under" equivalent of Home Depot for building stuff, some ink and other supply recommendations may be difficult to obtain in Wildcard's location, Australia

Good call. I didn't realize he was in Australia.

[Frog]

While he may have his "down under" equivalent of Home Depot for building stuff, some ink and other supply recommendations may be difficult to obtain in Wildcard's location, Australia

Good call. I didn't realize he was in Australia.

Yeah, it must be terrible to be teased with products that seem like salvation but are almost impossible to obtain some places!

Kinda' like what hardcore car and bike nuts go through when they see what is available in the European and Japanese markets, but not here.

[Wildcard]

I think we get the major brands here, for instance Ive been changing over from Sericol to Wilflex inks and while i love the colours, the recommended Artist Plus White has been tricky for me, i seem to turn it into more of a sandpaper white...

Anyway Im hesitant to completely rebuild the box but maybe its the only  way to go. Are there any really great plans available for a diy box with vacuum top?

[ABuffington]

Milliwatts, 30watts, 40 watts, 500 watts, 1,200 watts, 5,000 watts, 8,000 watts, 10,000 watts, 23,000 watts.  POP quiz can you name their sources?  and do numbers really matter? or wavelengths or any of that important stuff that makes emulsion expose?  Proper exposure has no slime on the squeegee side, very crisp line work, well formed halftones.

Short fast exposures may expose the print side, but the squeegee side is where the mechanical abrasion starts, if it's weak the screen will break down sooner.

Of all the do it yourself approaches, the sun is one heck of an exposure unit.  It is also the most unpredictable and a little easier with diazo emulsion since you can see the color change. LED is the future and works for most printers.  Like cars exposure units come in all strengths and sizes, some work better than others and often it is a matter of finding a system that fits your shop.  I wouldn't put an 8k metal halide in a shop that does short runs, conversely I wouldn't put fluo tubes in a shop with long runs.

Al