Step 5: Expose your screen, then rinse

Your screen is tucked away somewhere cool and dark to dry, so the next step is setting up your exposure rig.

A lightbox or light table, with several fluorescent bulbs set directly under a translucent piece of acrylic, allows for simpler set-up and shorter exposure times, but may take some experimentation to figure out what the correct exposure time should be. And hey, there's even an Instructable on making your own light table. Depending on what light intensity you have coming out of the lightbox, your exposure time could be around 4 or 5 minutes.

The setup I used for this project is just a 150W clear incandescent bulb in a socket with a long cord and reflector. A 150W bulb requires a much longer exposure time, but that's fine by me; it gives me a chance to take a break and get all my ink and fabric ready.

Before taking your completely-dry screen out, get the rest of your exposure rig put together.
You'll need some non-reflective black fabric, a sheet of glass or acrylic big enough to cover your screen, a ruler or tape measure, the light bulb, socket, and reflector.

With the light bulb & reflector all put together, hang it so that your bulb will be 12 inches (for a 10x14 screen) above the surface of the screen, centered. Lay the black fabric on the ground where your screen will be placed. Have your image-on-transparencies and acrylic ready, and check to make sure you've got the transparencies in the right orientation.

Since you're going to set the screen with the bottom side facing up, then lay your image and the acrylic on top of that, you'll be placing your image so that it's backwards when you look at the bottom side of the screen. This is especially important for text! (Think about it like this: you'll be putting ink on the inside of the screen and pressing it through to print. So the image you see from the inside of the screen is what prints; what you see when you look at the bottom side of the screen should therefore be the reversed image.)

Once the exposure rig is set up, take the dry, sensitized screen out and center it under the lamp, bottom side up. The black, non-reflective fabric should be underneath the entire screen. Arrange the transparencies with your images on the bottom side of the screen, then lay the sheet of acrylic over them to hold them flat against the screen. Check to make sure the distance between the bulb and the screen is correct. Turn on the light, expose for the correct amount of time, then turn off the light. Since I'm using a 10"x14" screen and 150W bulb, I exposed my screen for 45 minutes.

Once the exposure is finished, remove the acrylic and transparencies, then go rinse your screen. The kit directions for this step say "Apply a forceful spray of water (body temperature) to both sides of the screen. DO NOT USE HOT WATER." "Forceful" seems to be the key word here -- even the unexposed emulsion likes to stick to the screen fabric when dry, and using a strong shower spray or the spray-nozzle on a hose seems to work the best. As you spray, you'll see clear areas developing where your images blocked the exposure light; concentrate your spraying on those areas. You can rub the screen lightly with your fingertips, but if your image has fine details, you may lose some resolution by rubbing off extra emulsion around the edges of your image. Hold the screen up to the light; the mesh of the screen fabric should be entirely clear and open in your image areas. If it's not, keep on spraying.

Once your screen is washed out, let it dry completely.

Exposure chart for the Speedball diazo photo-emulsion system:
150 clear incandescent bulb
Screen Size 150W Bulb Height Exposure Time
8"x10" . . . . . . . . 12 inches . . . . . . . . . . . . 45 minutes
10"x14" . . . . . . . 12 inches . . . . . . . . . . . . 45 minutes
12"x18" . . . . . . . 15 inches . . . . . . . . . . . . 1 hr. 14 minutes
16"x20 . . . . . . . .17 inches . . . . . . . . . . . . 1 hr. 32 minutes
18"x20" . . . . . . . 17 inches . . . . . . . . . . . . 1 hr. 32 minutes

250W BBA No.1 Photoflood
Screen Size Lamp Height Exposure Time
8" x 10". . . . . . . . 12 inches . . . . . . . . . . 10 minutes
10"x14". . . . . . . . 12 inches . . . . . . . . . . 10 minutes
12 "x 18" . . . . . . .15 inches . . . . . . . . . . 16 minutes
16"x2O" . . . . . . . 17 inches . . . . . . . . . . 20 minutes
18"x2O" . . . . . . . 17 inches . . . . . . . . . . 20 minutes
<p>It shouldn't take a lot of scrubbing your screen to get it clean. Just make sure that you put the emulsion remover on when the screen is dry, let it set for 2 mins. then spray with water, the emulsion will come off easily like magic. If you have spread your emulsion thick and there are dried drips on the screen, you may have to do these steps a couple of times, but you still shouldn't need to scrub. Take care of your screens and they can be used for years.</p>
<p>Scrub your screen with comet ajax ete. Gives it some tooth. Rinse degrease with the best degreaser on the planet. Original DAWN dishwahing liquid. Dry apply photo resist</p>
<p>hi there I just want to double check how thick is your glass?</p>
<p>Does not really matter. I used regular window glass.</p>
<p>Trying to remove my image off the screen to use another design, is that possible or do I need to buy a new screen?</p>
<p>Use clorox bleach.</p>
<p>Once the screen has been developed aka exposed to light it is locked in and a new sheet must be used for each new design</p>
<p>Excellent 'ible with clear images and write up! I wonder about the spectral response of the sensitized Diazo - most photosensitive materials respond preferentially to certain wavelengths (colors) of light. If you can find out which, you could possibly build two illuminators - one of a color that will not affect the film while setting up, and another of a different color for the exposure. These could be built from readily available LED strips. Another advantage would be that LEDs generate a minimum of heat. You could possibly use a control circuit that can switch between LED colors using tri-color LEDs. BTW, you can trust this suggestion though I am &gt; 25 years old (about 3X) :)</p>
<p>where did you get your lamp from ?</p>
<p>You can use a construction style lamp with a metal shade that can be bought at any local home improvement store</p>
Every video I have seen on YouTube says it takes 10 minutes or less with an ordinary 60 watt bulb.
<p>Hi. Can you help me on &quot;Photo Emulsion for small images or letters&quot;, I find it quite complicated to print tiny image and letters. Please I really need to learn how to do it and I beleive that you can help me on it. Thank you so much! God bless. :)</p>
<p>Hello people, I'm new to silkscreen printing and I'm trying my first time out. i got the screen and i coat it with photo emulsion, printed my negative and then i expose it under the sun. however, after 40 mins, it doesn't seem to work. I'm not too sure where went wrong. these are the questions bothering me: <br>i) did i coat it correctly, is the coat too thin? <br>ii) i didn't place a piece of glass over the screen when doing exposure, is that why it didn't work? <br>iii) is the piece of glass over the screen necessary when exposing and can it replace with clear acrylic? <br>iv) what kind of light bulb should i use if I'm creating my own homemade light box for exposure? <br>v) what is Sensitizer? is it required for light exposure or just the photo emulsion is fine?<br><br>i hope to get help from pros like you guys.<br>Thanks so much...</p>
<p>Answers in order of how you asked:<br>I) It should be translucent to opaque in its coating...the more prints to be run, the more opaque. <br>II) The glass is only recommended for when exposing in order to burn the image to the screen in order to keep it as flat as possible. Clear tape can be just as effective depending on your set-up. <br>III ) No, as mentioned, the clear glass is not necessary.<br>IV) Depending on your lightbox set-up, for a small lamp/light-source (about 12 inches from the screen) a 150-watt incandescent bult or a BBA-1 bulb are the recommended. I personally use a small lamp with a 150 watt bulb. <br>V) Sensitizer is what is added to the photo emulsion to make it light sensitive to burn the image to the screen. And yes, it is required to make the emulsion light-sensitive so that the emulsion only under what was blocked washes out. Be forewarned though, once the sensitized emulsion is coated onto a screen, avoid allowing it to be in any light until you are ready to burn the image (which should be done under the exposure instructions.)</p>
<p>When I used cardboard in between the shirt front and back, I got ink smudged on the inside of the shirt. I have a tip: Since I am doing more than one T-shirt, I am using a glass cutting board sprayed with Elmers spray adhesive (to hold the shirt in place, since I am printing alone) in between the front and back of each T-shirt. I have had a lot of luck with this method (probably because the cardboard absorbed the ink through the t shirt layer, and the glass didn't) . </p>
<p>Just a note on the emulsion: I coat mine, making the last sweep outside, then let dry with outside down(on the pushpins), which usually lets the emulsion heave down as it dries (gravity), that way you are creating the thicker layer directly in contact with your film. </p><p>In your process , the thicker layer is on the inside, furthest away from the film during exposure, which may not resolve as much detail when needed. </p>
<p>Thanks for all the pics and great descriptions, really helped out in getting started. I was just wondering where you got the emulsion exposer chart as it caused me to mess up quite a few screens before figuring out the chart is wrong....in fact its REALLY far off :). diazos chart for a reflector set up should be set 18in (not 12) from the image and should be exposed for ONLY 7 minutes (not 45!!!!) after trying it with these numbers I get great results, trying it for 45 mins left me with an over exposed screen that was VERY hard to scrub clean. here is diazos chart for future reference...<br>http://www.speedballart.com/faq.php?cat=136</p>
thank you so much! im using the speedball system and ive never tried the photo emulsion process before. the insturctions they gave are confusing, but this cleared it up!
I couldn't believe how unclear the Speedball instructions were! Thanks for writing this.
I work for a screen printing company. You don't really need to use a flood stroke unless you are working with light colored inks, as they are thicker.
I work for a screen printing company. For a makeshift darkroom, find a room without windows, and replace the lightbulbs with bug lights. Bug lights do not emit UV light, UV is what exposes the emulsion. So you could have the room as bright as you want and not have to worry about exposing the screen. (I would still try to keep the light indirect)
Simple but very inspiring, so the process of screen printing can be done easily, thanks <br>http://www.belajarsablon.com
Holla,<br> Brilliant Instructable!<br> <br> <a href="http://www.instructables.com/id/DIY-Silk-Screen-Printing-Screen-Upcycling-Recy/" rel="nofollow">http://www.instructables.com/id/DIY-Silk-Screen-Printing-Screen-Upcycling-Recy/</a><br> <br> I have just posted an instructable on how to make your own screen printing screen cheaply and easily!<br> <br> :)<br> <br> -Emily
hi! i just wanted to let you know that because i like this instructable so much, i have added it to my silkscreen guide... <a href="http://www.instructables.com/id/silkscreen-printing-easy-and-cheap/" rel="nofollow">http://www.instructables.com/id/silkscreen-printing-easy-and-cheap/</a><br> <br> thanks for sharing your ideas!
How far does the ink stretch? How many shirts can I print with 16 oz of ink and a medium sized design? (roughly)
Could I print up a design like this on a t-shirt using this method?
if I&nbsp;may make a few suggestions I&nbsp;am a screen printer by trade and in order to save yourself lots of money on transparencies buy a can of dollar clear spray paint and do a light coat over your velum or tansparency let it completely dry the spray paint causes the black it to get solid and dark<br />
Wow, must be really cool to do this professionally!<br><br>Maybe you could answer this for me; I'm doing a screen print in my art class, but our classes are cut down to 20 minutes this week, so I can't burn my screen AND rinse off the screen in one class period. Could I burn my screen, then come back in 20-30 minutes to rinse the screen?
Hi there!<br><br>Some friends of mine suggested to expose dried emulsion under the sun. <br><br>Is it effective?<br>Anyone knows how long of exposure?<br><br>Please help!<br><br>Thanks!..:-)
yes but not on your body, better using a good quality heavy paper.<br>exposure is a little like sunbathing .. it takes a little experimentation to get just the right outcome .<br>makirro (the fool)
guys can you help me how to clean my screen...and whats the problem of my work every time i exposed my design..my design destroy pls help me......i'm using 4pcs 10WHATS lamp..thank you!pls help me<br>
This has been a lot of help to me.
when you do coating do you need to do in dark room ?
Can you use this method to print designs which are very colorful? or will the designs made with this method always be one solid color?
you can overlay a print of one color with another, or you can just cover some areas with masking tape and print with one color, and then vice versa and print with another color
is it possible to expose the screen outside on a sunny day, instead of using a light rig, like in a similar instructable?
yeah, definitely possible, but it's very dicey. there are a lot of factors that play into exposing a screen with sunlight--weather conditions, if it's cloudy or windy.<br><br>i find it easier to just use a bulb, that way i can do it any time and it's always consistent!
if you have a design that's bigger than 8.5x11, or you don't want to go through the hassle of getting something copied onto a transparency, it works just all well to do this:<br><br>take a copy of the image and cut off some of the extra white paper around it. paint the piece of paper with baby oil. let that sink in and then dab off the excess oil with a paper towel. this makes the paper translucent, which works just as well as something transparent.<br><br>you might have to bump up the exposure time a tiny bit, but not too much. (i couldn't tell you HOW much because i've never actually used transparencies when screenprinting)
Just a hint for people who can't work out the exposure times. <br /> <br /> You can put a strip of emulsion on a screen and test like you test in darkroom photography. Block most of the strip with something light proof (a bit of cardboard) but leave a couple of c.m. hanging out. Start exposing. After a couple of minutes move the cardboard back so another couple of centimeters is showing. keep doing this every minute or so, until the max time is reached. Then wash out as usual. this way you can see which time works best and you don't have to test on like twenty screens.<br /> <br /> I hope this makes sense. and is helpful to all those having trouble<br /> <br /> Peace <br /> <br /> Jake 1NE.&nbsp; <br />
ugh, i wish i would've done this before doing emulsion FOUR TIMES on a 20x24 screen until it worked.. this would've been so much simpler..
I used to work at a screen printing shop and we didn't use liquid photo emulsion, we had big rolls of emulsion sheets that were stuck onto the screens with water and left to dry in a dark cupboard. I would cut the huge sheets into 12" x 14" squares which would be put in a drawer away from light, while the huge sheets were essentially a roll stuck in a big black tube (to block the light). The emulsion sheets were pretty much just a plastic sheet with emulsion on it that would stick to the screens with water and when the emulsion dried you would peel off the plastic sheet before "burning" the logo on the screen. When the "burning" was done (on a vacuum sealed light table with timer) I would "blow out" the design with a pressure sprayer, then dry the screen, tape the edges and fill any defective holes with liquid emulsion.
In junior high my shop class did silk screen printing with that kind of emulsion on plastic - only we would put our piece of emulsion plastic-side down and cut and remove the emulsion with an exacto knife. When the cutting was done we would attach the emulsion to the screen with water, let it dry over night with pressure on the screen, peel off the plastic and then print. The teacher had basically been printing that way for 25 years, with very good results.
you did silk screening in JUNIOR HIGH!? i'm jealous!
I see. Well yes I did cut the emulsion while it was still on the plastic, its the same as you have done here but we did not put pressure on it during drying off. The shop i worked at was run by an old couple in their 70's who've been doing it for nearly 40 years. I'm still really proud of that job. How many people get to say "I was a graphic designer at my first job when I was 15." lol
Neat, I'd love to have the chance to play with that kind of equipment sometime. And I'd imagine that the sheets are a whole lot easier to work with (and less hugely messy) than the liquid emulsion. Envy!

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