How strong is too strong?

[screenxpress]

How strong is the pressure washer you use for washing out exposed screens?  I got a 1700 psi thinking that would not be too strong for throwing spray outside the washout booth. I was wrong. It leaves a nice mist around. So what's the most popular?  Tks.

[Frog]

Well, I don't use a pressure washer, but in the Douglas Grigar Coating for Maximum effect article on the home page, he noted that
All photos are of stencils that are fully exposed and developed with a 1,000-psi pressure washer at 30-36 inches.

[3Deep]

I have a garden hose hooked to my sink with a multi head sprayer and when the halftones/finelines get a little tough I use a spot remover gun with water in it. 

[Frog]

For thirty years, I have used something like this

[bimmridder]

750 psi here

[screenxpress]

I've been using the garden sprayer but now with a real washout booth I wanted to step up.  I think I stepped larger than I needed.

[Frog]

too much pressure can even stretch mesh and reduce tension (if not tear it)

[blue moon]

we use 1400-1900 depending on what's available. The emulsion is holding up on the 110's even with the head 4-6" away from it. On 305 and 330's we keep it about a foot away. Finer dots need longer time to open rather then getting closer. Sometimes I'll turn of the power and just use regular pressure but get within an inch or so. This is mostly when there are adjacent areas that would otherwise get blown out by high pressure.

So over all, 2000 or less has worked fine for us. We'll most likely get a Camspray later this year and looking at something between 1500 and 2000 PSI.

pierre

[screenxpress]

we use 1400-1900 depending on what's available. The emulsion is holding up on the 110's even with the head 4-6" away from it. On 305 and 330's we keep it about a foot away. Finer dots need longer time to open rather then getting closer. Sometimes I'll turn of the power and just use regular pressure but get within an inch or so. This is mostly when there are adjacent areas that would otherwise get blown out by high pressure.

So over all, 2000 or less has worked fine for us. We'll most likely get a Camspray later this year and looking at something between 1500 and 2000 PSI.

pierre

I was mostly trying to keep my environment dry and still pressure the screens.

[Frog]

Shape of the spray pattern is another important variable.

[tpitman]

I've used my pressure washer to wash out the image. A few years ago I took a seminar at an ISS show with Charlie Taublieb who said that if your stencils are fully exposed, you should be able to wash them out with your pressure washer. That doesn't mean a pencil-thin stream, but rather open the nozzle up to get what's more like a wide, strong fog. The idea was to have enough fine droplets under pressure to clear out the tight detail areas of the stencil. I've got an el cheapo Home Depot washer that's about 1500 psi.

[jsheridan]

If all your chemicals are doing their jobs, all you need is a high pressure rinse in the 750-1200 range.

To many people overuse the pressure washer for a lack in chemistry.

[squeegee]

For development we use a pressure washer with a fan spray, usually a foot away or so, it works fine, it's pretty strong, 1000+ I'd say.  Also have a sprayer I purchased from Majestech (now Saati) that resembles Frog's but is made of copper, it makes a fine point spray, it's awesome for stubborn areas, or fine detail with lowered pressure.

We develop, store, burn screens all in one room (coat and dry in another), A/C and dehumidifier controls the enviroment most of the time, but for when they don't I have considered putting in a  curtain between the washout area and the rest of the room, like those clear curtains you'd see on the door of a walk-in refrigerator.  Haven't gotten around to that yet but it's on my list.

[ZooCity]

We use a Camspray 1500a for developing and for reclaiming.  I'd say it's about perfect although I'd like to try out some different nozzles.  There is still some misting going on.  My best suggestion would be to simply ventilate if it's a nuisance with the 1700psi.  Alternately, look into a unit with higher GPM and lower pressure. 

In my ideal shop there would be:

• A lower-pressure <1500psi unit with a 20" wide fan spray that is consistent in pressure across that width, next to it's own dedicated booth for developing screens.
• A higher-pressure <3000psi unit for blasting out emulsion at reclaim, again in it's own dedicated booth for reclaim with a filtratrion/recirc system for the water.

Why the high pressure for the reclaim one?  Well, I think you could get a wider spray that is still strong enough to process screens quickly with a more powerful unit.  Also, Colin talked with me once about using a high-power pressure washer to "massage" mesh and essentially work-harden it at reclaim.   I think the extra heave-ho would help with ghosting and stains to by agitating the knuckle areas of the mesh a little. 

[alan802]

We got a 1200 psi and it's a beast, but I wouldn't want it to be any less powerful.  We need all that power and I don't think 1700 is too much.