Water Stains

[ebscreen]

For a couple weeks now we've been getting water stains on a couple screens now and then.

Nothing has changed on our end except ambient conditions. I do remember a couple months
back that the water department made a release about an algae bloom in our water supply that they were
going to begin treating. Wonder if it's connected.

At any rate, I found this post by Rockman (someone should invite him)

http://forums.screenprinters.net/viewthread/2/338867


So I guess we'll leave screens standing tall for a bit now. But I'm wondering if there's a better option.
Filters? Wet-dry vac with screen attachment?

Lastly, would it be illegal to setup some sort of automated bot program type thing to harvest all of the
posts off of the old board and host it on a new site or something? We had an embroidery question
the other day and a quick search of that site yielded a post (and solution) by our very own Inkman.
Hate to lose that resource.

[alan802]

Are you talking about after exposure and sprayout, or after reclaim?  After exposure, we use an 18" window squeegee and swipe both sides of the screen when finished spraying out, then I hit the image and screen with compressed air for 10-15 seconds, and finally set it upright in front of a 42" heat buster fan and the screen is ready for taping in less than a few minutes.  We really don't have to do any of this stuff when the screen is exposed long enough but we usually need the screens turned in a hurry so the faster they dry the better.

[ZooCity]

Wet vac works pretty well for us.  I still haven't built a special attachment for it, just using the included one, sanded down smooth so it doesn't hurt the mesh.  It doesn't pull a ton of water off or actually dry the screen much but the vac sort of vaporizes it and disperses it.  It keeps the spots off.  Clean compressed air would work just as well I'm sure but it'd have to be very clean I would think. 

Biggest thing is to have your drying cab warm and moving before putting the screens in.  If it's cold in there or you don't turn the vent/heater on in the cab you get the spots. I think that's why rockman's solution was to stand them upright as the spots tend to appear when the water has a chance to pool for any amount of time. 

Last idea would be a simple water filter, probably wouldn't need anything fancy. 

What do you degrease with?

[ebscreen]

After reclaim, before coating. Though I've seen weird marks post exposure/drying as well.

Looks like the type of films/rings/stains one might hear about in a dishwashing soap commercial.

The horrors of an unclean bowl....



I wouldn't trust any compressed air to be clean enough to hit a degreased screen. Hold your
hand in front of an outlet if you don't believe me.

Good point on the drying cabinet, I think you might be on to something. I got the feeling
it had to do with something of the sort as it would fluctuate with ambient temperature.

Been meaning to get a vac in anyways, maybe I'll give it a whirl. Cheap water filter might not be a bad
idea either.

[ZooCity]

Just try the immediate hot box approach first, that might solve it.  I really think that if you keep it from pooling you avoid the spots. 

I like the vac idea because it does pull some water out and we even use a shamwow around the rollers before going into the box.  The way I see it, there's no reason to introduce any excess water when your goal is to get things try. 

If you filter, let us know what you use.  I imagine you'll need to be fairly religious in replacing the filter though or you'll get more problems than you might solve.  I think I have too much pressure in our new wash room (3/4" pex originating very close to the building main) to use most of those devices in-line.  I had to upgrade to some 'high-pressure' hoses when I first finished plumbing as they couldn't hack it. 

[Shawn (EIP)]

I only see water like stains if I'm in a rush do not fully rinse out the degreaser. Maybe spend more time on the final rinse?

[nobrainsd]

Ha! Nice to see my old avatar referenced here on the coolest screen printing forum. I am just a lurker at the moment. Still print, but it isn't my focus at the moment.

I definitely had some issues with hard water deposits on my screens. Everyone who surmised that the stand them on edge trick worked because it kept water from pooling and spotting on the screen is correct. Just enough runs off to make the screens work for me. A vac sounds like a quicker solution, but I only do screens in batches of 25 so it wasn't that inconvenient.

I built a screen drying room and it has a dehumidifier in it. Simply having the room ready is a good idea, but I had issues even with the room nicely prepped. I'm not leaving them out for long. I'm sure that might be a problem if your space isn't relatively clean. Hard water sucks. My water quality fluctuates.

[tonypep]

Wet dry vac with the right att is best but squeegee is good enough. Also sounds like you're slightly underexposing

[Frog]

Also Sean, you know that where you are, you don't get the good, consistent water from EBMUD that you had in Oakland.
As the weather warms, more slightly saline water from the delta is added to the mix.

[ebscreen]

Thanks ya'll.

Nobrainsd I'd like to invite you to our forum. Oh wait.


I'm thinking either a carbon filter or a rough micron filter might be in order.
Used to use them in various stages of brewing, so I have a few around. Worth a shot
I suppose, though you're correct about  changing them frequently.

Screen kids are instructed to flood screens with a ton of water from top down as last
step after degreasing, so I'd be amazed if it's residual chems.

Pretty sure it's not under exposure, I've seen that before and this has more of a rock
salt type look as opposed to a rainbow sheen. Also, I just examined a screen that we had ganged,
waterbase rinsed  out of first side, dried in sun, and it's got a few mineralish rings to it.



Yep, never saw this in Oakland Andy. Saw a lot of things, but at least the water was consistent.

[ebscreen]

UPDATE!


Instructed the kids to stand the screens up for a minute before going in the cabinet.

Presto, no more water stains.



Bugs me a bit as I had always been adamant(ium) about going straight from the degrease
to the box to avoid ever present falling dust. This will work for now, but I'll think about getting a vacuum in,
though another thing to watch/maintain/provide electricity to doesn't sound very appealing.

[mjrprint]

You sure it is water stains? Could be scumming from underexposure.

[ebscreen]

Post degreasing, pre coating, not post exposure.

Hard salty mineralish looking rings. Not no more.

[Frog]

Like I reminded him, the water company in his area is known for undrinkable water (when not filtered) and it gets worse as the weather heats up because they mix it with somewhat brackish water from the Delta where the bay water and Sacramento River water mix.