What Am I Doing Wrong Burning Screens!!!

[hjlanda22]

Ok we are new at this (we do signs) but after alot of heat pressing t-shirts we now have moved into screen printing so heres the problem I recently had a baseball team I had to do the jerseys 20 of them so I thought GREAT perfect time for me to try the screen printer. We use photoshop print the simple text (large block letters) on a trasparent using the epson 4800 Pro with special screen print blackout inks installed so as to make sure no light gets through we also use a program called fastrip.

The screen.... we cover the screen with premixed emulsion (the kind you dont have to mix) using a troft style tray that the screen suppliers sell in order to get the emulsion coating on the screen properly. (oh yes prior to this we did degrease the screen and left it overnight for drying as it was the end of the day anyhow) We coat the screen in a light safe room. let it sit laying flat (nothing touching the emulsion)

NEXT DAY...... we lay it flat on the table also weigh it down to ensure it is flat agianst the image we want to burn. Leave it for 5 min (we have also left it for 30min) we take it from the table and you can see a ghost image so we are thinking sucess! But when we take it to be presure washed out it never just takes out the burned image it starts removing emulsion from other areas also, and the image that we burnt looks horibile! never clean lines.....

I am not sure what I am doing wrong?????? the emulsion I used was brand new out of the box is it possible the emulsion is bad???? is the presurre washer to much power??? I just dont understand what I am doing wrong here, we have repeated this process 5 times each time reclaiming the screen , we have also used another screen and we are getting the same results any advice would be appreciated

Thanks in advance
hjlanda22

[iSign]

I think the pressure washer is the problem. You only use that for reclaiming the screen. For rinsing out the emulsion from your image, just put your thumb over a hose for a minimum of pressure, & work fast. You need to get the image cleaned out in 3 or 4 minutes & then have some newsprint to gently blot the excess mointure off the screen. The water softens the emulsion even in the burned areas, so don't leave it wet. At least that's the way I did it. Have you kept you emulsion in a cool dark place? You coat the print side of the screen with a decent thick coat? Can't see any holes before burning? (You can use a yellow bug light in the darkroom to be able to see a little)

Also, what is your light source? I'm more used to 1 or 2 minute exposure times.

[Simon Belmont]

question 1: does the emulsion clean out well, or are you left with a stain?
question 2: have you used an exposure strip to test your burn time.


the pressure washer could be a problem, but if you are exposing spot colors it will work as long as you burn the hell out of the screen and stand about 5 feet back.
Like isigns, I'm used to 1-2 min exposure times, but if you don't have a vacuum exposure table i could see why you are so high.

[Pro Signs & Graphix]

NEVER use a pressure washer to make a stencil. As iSign states water is all that is needed. Considering the newness to making stencils, consider using a trigger spray bottle. It will give you much more control.

Also, absolutely ZERO white light when making the stencil (except in the exposure unit). A 20 to 40 watt yellow fluorescent bulb would work fine and not hurt the stencil.

When we were screening, we found that the liquid emulsion was a pain. Never could develop the knack to get a nice even coat. For this reason, we used the Ulano films. The films made stencil making easier (for us). They also included an exposure chart so that you would know what to expect.

As for the expected "burn-time", it sounds as if you are using one of those homemade fluorescent tube boxes. If you are, forget it. Use it for a light box or walk it out to the trash. Even though they are capable of burning screens the amount of time required is ridiculous. What would take one or two minutes on a professional unit will easily take 30 to 45 minutes. You really lose when there is a mistake. If you cannot afford to buy a professional vacuum assisted unit, make one with a metal halide light source (minimum 400 watts).

Lastly, did you get and exposure scale yet? If not, get it it. It will save you more grief than can be imagined.

[Cadmn]

use unfiltered Black ligh tubes in your fluorescent fixture

[hjlanda22]

Ok Thanks guys I think the preasure washer is the problem then. no its not a floresant light table it is a home made exposure unit that uses a buld that is very high powered (ok, you know when you go to the football games you and its dark, high school game well the light bulbs that light the field at night are these huge bulbs right, one of those are what burns the screen. The previous owner of my equipment built it and used it for many years trouble is he is on vacation right now and his father whom answered the phone was unsure why I was having the problem. I belive if I remember correctly when I picked up the equipment he told me 5 min max on the burn time but then agian my memory really sucks......

So after burn, what is the best method of washing out a screen to reveal your image. (I watched these videos that showed washing the screen with a preasure washer that is why I did it this way.


:thankyou:

[hjlanda22]

question 1: does the emulsion clean out well, or are you left with a stain?
question 2: have you used an exposure strip to test your burn time.


the pressure washer could be a problem, but if you are exposing spot colors it will work as long as you burn the hell out of the screen and stand about 5 feet back.
Like isigns, I'm used to 1-2 min exposure times, but if you don't have a vacuum exposure table i could see why you are so high.


yes the emulsion does clean out well in the burned area however the edges are torn up not clean so to speak

no I dont even know what an exposure strip is....... Where do I get this?

[Pro Signs & Graphix]

I belive if I remember correctly when I picked up the equipment he told me 5 min max on the burn time but then agian my memory really sucks......


Forget the memory, you need an exposure scale to properly determine exposure time. There are no ifs, ands, or buts about it - it is a must have. To complicate matters, unless you are fairly good at coating screens evenly EVERY time, your exposure times change. This is why we mentioned the films.

It sounds as if you are running a homemade M-H, which is better BUT also requires a warm-up time to be at full output. This means that you MUST have a "blocking door" that prevents the light hitting the screen for the first five minutes that the lamp is on.

Your lousy edges are directly attributed to exposure AND wash. Again, try the spray bottle.

Do you have the book "Printing T-Shirts for Fun and Profit"? If not, you should have it. It will give you a better understanding of the process, hit and miss gets frustrating and expensive (as you probably know). Personally, screen printing is PITA - I hated it. Nevertheless, it is still another learning curve that takes a while to get a grip on.

BTW, what press are you running?

[Pro Image]

What kind of elmulison are you using? How many coats are you putting on the screen? Is the elmulison thicker in some areas or is it a even coat on the screen? What is the mesh of the screen? I need these answers to help you with.........

[hjlanda22]

Forget the memory, you need an exposure scale to properly determine exposure time. There are no ifs, ands, or buts about it - it is a must have. To complicate matters, unless you are fairly good at coating screens evenly EVERY time, your exposure times change. This is why we mentioned the films.

It sounds as if you are running a homemade M-H, which is better BUT also requires a warm-up time to be at full output. This means that you MUST have a "blocking door" that prevents the light hitting the screen for the first five minutes that the lamp is on.

Your lousy edges are directly attributed to exposure AND wash. Again, try the spray bottle.

Do you have the book "Printing T-Shirts for Fun and Profit"? If not, you should have it. It will give you a better understanding of the process, hit and miss gets frustrating and expensive (as you probably know). Personally, screen printing is PITA - I hated it. Nevertheless, it is still another learning curve that takes a while to get a grip on.

BTW, what press are you running?

Exactaly It does need to warm up I know that and it does has a blocking door that prevents light from hitting it I have to remove it in order to expose the screen.......

The press is a manual press not sure the brand but it is a 4 station 6 color press Looks like and octopus also have the flash cure heat thing and the convayor belt drier. no I dont have the book you mentioned.

[Pro Signs & Graphix]

no I dont have the book you mentioned.

Then stop what you are doing and get that book. It is like driving with your eyes closed. DO NOT be fooled that it is just so easy. There IS a learning curve that is on par with the learning curve of your inkjet printer, and maybe more because there is less automation and more "technique".

[onesource]

Run water over the screen and rub the image away with your hands then spray a little pressure to clean up the image area. No pin holes and the edges should be crisp. I am still burning with sun light on pretty days. 30sec. - 60sec. exposure time, I use 60sec. on cloudy days. exposure time is critical, I think 5 minutes may be too long with some lights and not long enough with others.
Hope this helps.

[High Octane]

real light water pressure....more of a shower then a blast....hit both sides and let the emulsion loosen up.

[vid]

[quote=onesource;168805]............I am still burning with sun light on pretty days. 30sec. - 60sec. exposure time, I use 60sec. on cloudy days. exposure time is critical..........[quote]

HHHHHHHHHHHHhaaaaaaaaaaa, you're cracking me up. LOL. When I did that stuff, I had my exposure times scrawled on the door frame for time of day and time of year exposure settings. It mystifies people that with some practice you can hold a consistent dot with a "solar" exposure unit. Not the best practice, but it works, huh?

[mladams7259]

make sure the room you are leaving the screens to dry in is not humid. the screens will not dry properly in a humid room. even a little can screw up the process......

[Ian Stewart-Koster]

Vid & Onesource, we use the solar UV light supply too. You can get a feel for it after a while!!! 10 am morning sun's best here. The emulsion & type of positive governs a lot too.

HJlanda, if you wet the screen after exposure, wet it with a sponge or flannel gently, and sthen prinkle water on it- the unexposed emulsion should just fall out, esp. if you do it in the shower, or with a GENTLE garden hose.

[Signguyno1]

We make screens often in our small shop with shop made eqipment. We use Nazdar QFX for t-shirts as well as decals as liquid coated emulsion. Make sure that the screens are dried in a flat condition, cold and high humidy have a great deal to do with the drying process, when dried well are stored in a cool, dry, dark area. Never expose coated screens to sunlight or flouresecent light before exposure. Clamp your screen over positive or negitive on your exposure table and expose to light source, we use a carbon arc lamp for depending on emusion used anywhere from 2-5 minuts. Developing or wash out (not with a pressure washer) with cold water to warm through a hose with a adjustable nozzel (available through silk screen suppliers) after developing, blot with newsprint (old news paper) blow off with compressed air to remove risidual moisture and dry with forced air (window fan) when dry touch up, blockout and tape.

[GVP]

When you say you weight it down, are you just putting weights on the frame? You need to press the mesh against the glass of your exposure unit otherwise light will creep under the edges of your positive and you will definitely not get clean lines. Vacuum would be best, but you can make a wooden block to fit inside your frame and cover one side with foam rubber - insert with foam against the mesh and then put a little weight on the block to ensure intimate contact.

Also, as others have said, no no to the pressure washer. A light spray both sides of the screen and let it stand for a few minutes. Then a firmer spray to clear the openings, again from both sides. When clear, blot to make sure no liquified emulsion settles in any of the fine detail.

[JUST-IN-ADVERTISING]

Sounds like overexposure to me ... 5 - 30 mins .... holy overexposure batman your images will never wash out...try less time ....

~just my thoughts

[dclet]

ehh lots of variables

your positive - not dark enough?

too much photo emulsion - you only have to skim it, do both sides to pull the emulsion completely through the screen...will also occasion sand the screen lightly...

exposure - most premixed stuff is very forgiving and we rarely do anything longer or shorter then 10 minutes. Be sure the positive is in complete contact with the screen.( we use a piece of 30 mil magnetic(dark side down), then piece of celtec or cardboard and then black cloth and then paints cans to weigh it down. :)

wash out - we use warm water, hit the screen both sides let it sit for 30 - 40 second - then start really washing it out. I like to blot it during wash out with a paper towel to check it. We use a adjustable shower head connected to the sink. Go slow and keep an eye on what you are doing..blot excess.. let it dry completely.


My bet is the emulsion ( either not dry and too thick ) or the positive...your not seeing it wash out... so your blowing through everything....

[Scubadog]

Pro is right get the book, it is a screenprinters bible.

[javila]

Too much emulsion, and too much water pressure.

Coat the screen once per side with the scooper and a good amount of pressure(so as to not leave alot of emulsion on the mesh).

When you wash out the screen use a regular hose adapter sprayer. Soak the screen lightly and let it sit for a few minutes. Then go back with mild pressure to clear the stencil.

You biggest problem sounds like too much emulsion with not enough time. (what mesh are you using?)

[K Chez]

I'm suprised that no one mentioned the fact that there are many different types of light (ie: spectrum) that will affect exposure. Different types of light will take different times to properly expose the same emulsion.
Doing some exposure tests is a MUST especially if you're just starting out. Another biggie is consistancy in coating the screens-the same number and sequence of coats. The thickness of your stencil is directly proportionate to the thickness of the layer of ink that you're laying down.

[d fleming]

Pressure washer is for reclaim only. I use a shower type adjustable nozzle from hardware store on the end of hose for washing out, saves my wore out old thumb. Do a step wedge test to determine proper exposure. Make sure your film positive is firm against screen when exposing. Nasty edges could be from undercutting. Emulsion is fine, I've used both films and emulsions over the years and they both have their advantages/drawbacks. Been using strictly emulsion for quite some time now, no problems for simple or high end jobs. Wouldn't recommend blotting fresh washed screen with anything. Use an air hose to blow off excess and to make sure you avoid scumming in open areas.

[schurms]

Cut vinyl and use that.

[Cadmn]

Sounds like overexposure to me ... 5 - 30 mins .... holy overexposure batman your images will never wash out...try less time ....

~just my thoughtsthe point is it's all washing out so underexposure is more like it since you are right overexpose & nothing comes out

[onesource]

It's the first way I learned and I good at it and then I learned the other ways later, but yeh it works and very well. Old thread but I wish you could still use bleach to clean a screen.
I stopped screening altogether now and I just sub it, I wish I woulda done this years ago! [quote=onesource;168805]............I am still burning with sun light on pretty days. 30sec. - 60sec. exposure time, I use 60sec. on cloudy days. exposure time is critical..........[quote]

HHHHHHHHHHHHhaaaaaaaaaaa, you're cracking me up. LOL. When I did that stuff, I had my exposure times scrawled on the door frame for time of day and time of year exposure settings. It mystifies people that with some practice you can hold a consistent dot with a "solar" exposure unit. Not the best practice, but it works, huh?

[iSign]

ya'll realize you're talking to someone who hasn't posted here in 6 months?

[onesource]

Everyone else will read it and laugh too!ya'll realize you're talking to someone who hasn't posted here in 6 months?

[K Chez]

Damn, I have to pay attention more!!!

[Ian Stewart-Koster]

I keep going back to his first post in this thread- and after 5 tries it's still not right...I wonder if he actually mixed the sensitiser with the emulsion at all- or not!?