TSB
screen printing => Screen Making => Topic started by: Maxie on February 06, 2016, 12:16:15 AM
-
I'm sure this has been covered before but what is the ideal temperature for drying screens?
-
75°-80°F > 20-30% relative humidity. Somthing in that area. Things are different for everyone, but this is a good base line.
Murphy
-
My little 5x5 space stays at 90-95 degrees and 15-20% humidity.
-
We have a 7" x 7" room that, according to my wireless thermo/hygrometer that reports directly to my desk (and I don't entirely trust 100%) we are usually between 100 and 115 degrees, ~7-18% RH. It might seem a little hot and a little dry, but that room is in use all day long for drying freshly degreased screens, freshly coated screens and freshly developed screens with a 150-200 screen a day throughput. I try to keep it as hot and dry as possible because the door gets opened a lot, and there's a lot of water to pull out of the air.
We can dry an entire rack (about 18 screens) of freshly coated mixed 150-S, 180-S and 225-T in 20-25 minutes or 100-150 soaking wet developed screens in about 45-60 minutes with no wiping, no vacuuming. The rack of degreased screens takes about 15-20 minutes to be ready to coat. It depends on how much the room is being utilized by "the other guys."
I don't know what I'd do without that room.
-
above 85-90 degrees F and you'll start to have issues with Diazo emulsions dark curing if they're at that temperature too long.
-
Do you have any issues with the mesh relaxing at all in that heat?
And like jvanick said, any issue with pre-exposure due to heat?
Personally I don't like to see the heat above 90 degrees, but I have my screens in an enclosed box that we move racks into and out of.
-
Our drying cabinets are set to 90, but we dont run them long. Never had a issue.
-
but we dont run them long.
key words here...
we run at 90 for an hour or 2 tops if trying to 'fast-line' screens through, but then store at 70-75 degrees, 25-30% RH.... Typical tho is that we just coat the day before, let them dry in the 70-75 degree screen room and away we go.
-
Do you have any issues with the mesh relaxing at all in that heat?
And like jvanick said, any issue with pre-exposure due to heat?
Pre-exposure? Not at all. We use Aquasol HV photopolymer+ diazo sensitizer.
As far as mesh relaxing? Never tried it any other way, but I do suspect that fresh stretches lose more initial tension this way. We've never had any problems in the shop because of it, though. Also, every fresh stretch gets retensioned the first time it comes back through the reclaim loop. Then once every two weeks or four weeks depending on how long it was sitting and how many prints it dealt with since last retension.
Seems to work out pretty well. Once work-hardened (as much as you can work-harden a roller) and retensioned two to four times they stay pretty consistent...depending on the mesh in question...once at this point we check the tension and they are usually still well within tolerance and will probably not need retensioning again until it dies from lazy handling in the shop.
Also, we do process everything through that room at a very rapid pace. Only fully exposed and developed screens tend to stay in there for more the thirty minutes at a time.
-
SBQ emulsions like Aquasol HV can withstand 100 degree drying conditions with no ill effects. This is a big reason why SBQ is popular in hot areas.
As Jason mentioned, any diazo should be kept at 80 degrees or lower to prevent dark hardening of the diazo. If you add diazo to HV you must store it now at 80.
Drying time is relative to humidity. Lower humidity = less time and faster exposures. High Humidity = more dry time and longer exposures.
In Phoenix in summer, HV exposes in about 30-40 seconds on a 5kMH. Along the coast of California in summer with fog and overcast this goes up to 60 seconds. Exposure is shop dependent. The ambient conditions in one shop are different than another, it pays to dial in your shop and ignore how long any one else exposes for.
Al
-
The golden egg is a room at 72F at 18% humidity year round, 24/7