AHS Screen Printing: PRINTING WITH OIL-BASED INK-- demo review, practice assignment, and how to print light onto dark!

In yesterday's 20-minute OIL-BASED INK demo, you learned some of the differences between oil-based and water-based ink, the main one being that oil-based ink requires HEAT to dry/cure fully, which affects a lot of different things:

* printing

* clean-up

* classroom cleanliness!

etc etc etc etc etc

Things I mentioned during the demo (and which were listed on the board)

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PRINTING ON A T-SHIRT REQUIRES:

1. Specific layouts when burning a screen (where you expose the stencils)

2. Different registration steps

3. Special techniques when printing LIGHT ink onto DARK fabric, including use of the "FLASH DRYER" (!) (so exciting!! :)

4. Different CLEANING steps-- NO OIL SQUEEGEES IN THE SINK! etc etc etc etc etc

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,,, #s 1, 2, and 4 are things we'll discuss/learn another day.

TODAY, I showed you #3-- what YOU will do to PRACTICE printing with oil-based ink, on t-shirt fabric. Actually, a piece of a "test square", which is basically fake fabric that printing companies use for their t-shirt test prints... but it's similar to fabric. Mostly.

Anywayyyy....

info, review, and highlights...

1. You will practice printing oil-based ink with your LARGE VELLUM stencil. By that, I mean the stencil on your screen that was created from the large vellum positive of your sticker design. Mask off EVERYTHING on your screen (on the squeegee-side!) except for the Large Vellum stencil. TRUST ME! This will enable you to print two stencils, with different inks, without having to clean your screen in-between. Oil-based ink doesn't dry out-- you can leave ink on your screen and clean it another day-- and if you mask-it off correctly, you can print different colors without having to clean in-between! You'll see :). (I'll demonstrate this as prep before you do 'foil transfer printing')

a screen fully masked-off to print one stencil and keep the rest of the screen "clean"

2. Oil-based ink squeegees have a softer blade than the ones we use for water-based ink. You can identify them by their color: dark blue for water-based, and yellow (or sometimes green) for oil-based. DON'T MIX THEM UP!

for now, or any time when some students are working with water-based ink, make sure you are using the correct one!

3. Oil-based ink is easier to work with because it doesn't dry naturally, but a massive pain because of this, too-- because if it gets on a surface, it STAYS WET and will transfer onto another surface if touched-- like your hands, your substrate, and even your clothes. I'll show you how to (hopefully) get unwanted ink out of clothes/fabric substrates later, but if it gets on your skin while printing, etc, USE THE POWDERED SOAP IN THE SILVER DISPENSER. It's fantastic. It's called Boraxo, and gets most ink off of your skin, but especially oil-based (which isn't really affected by normal, liquid soap)

4. Oil-based ink is thicker than water-based. Some are extremely thick (depends on the color). You will use a craft stick to SCOOP out the ink from the tubs and put it on the screen (whereas you poured out the water-based ink, from jars, using the stick to help guide the ink).

5. You will first practice oil-based ink by printing three different ways on a piece of t-shirt "fabric". Instructions are up on the board, but the gyst of it is this:

FIRST PRINT (left, on the above example):
Just one pull. Dry the ink in the conveyor dryer. The ink won't be completely opaque (if printing on a light substrate), and may look slightly faded (if printing on a dark substrate). This is because, when using oil-based ink, the first pull does not (usually) release all the ink from the stencil. It can be a desired, 'distressed'/worn look, but generally, you always want to make TWO strong pulls. So:

SECOND PRINT (middle, on the above example):

Make two strong pulls. (Remember-- NO BACK-FLOODING!) This will release all the ink from the stencil and make the ink more opaque than before. If you need to make a third pull, do so. Dry the ink in the conveyor dryer.

THIRD PRINT (right, on the above example):

Make two/three strong pulls, flash-dry, THEN print another layer, then put the whole thing through the conveyor dryer..

WHY??

If you're printing light ink on a darker fabric, the ink won't be opaque/true to color unless you flash-dry between layers. This is because the ink will just keep soaking through the fabric, it won't build up/get thick/be opaque (unless you're not printing correctly and the ink prints too thickly.

If, however, you FLASH-DRY after your first (two) pulls, this surface-dries the ink so that the next pull/layer will sit on TOP of that ink, and give it the desired opacity.

some inks are naturally more opaque than others, and you might not want/need to flash-dry
between layers when printing your project(s)

FLASH-DRYING is easy-- just requires placing the flash-dryer over your substrate, on the platen, for 30 seconds or so, until the ink is dry to the (careful) touch.

the DIFFICULTY comes in printing the next layer, after flash-drying...

you have to CHECK TO MAKE SURE THE SCREEN LINES UP WITH THE PRINTED INK, before you pull another print! If it doesn't line up PERFECTLY, in all areas of the stencil, you will end up printing a DOUBLE-IMAGE. Which very, very rarely actually looks good.

HOW DO YOU PREVENT THIS?

*1. make sure nothing moves, BEFORE you start printing: the screen should be tight, the platen tight, and the fabric substrate WELL-ADHERED with the red platen adhesive

*2. After flash-drying the first layer, CHECK to make sure the stencil lines up with the print, by lowering the screen and carefully pushing on the screen (like when you check the off-contact), to see if it lines up. Check ALL areas of the stencil.

*3. IF IT DOESN'T LINE UP PERFECTLY... figure out what moved. If it was the screen or platen, you can probably move it back into place.

*4. IF IT DOESN'T LINE UP PERFECTLY BECAUSE THE SUBSTRATE MOVED... Game over. Just have a less-opaque print, it'll be fine. DON'T PRINT THE NEXT LAYER IF IT DOESN'T LINE UP! *ALSO*-- get Miss Doezie for help before you give up, OR if you are unsure if it's lining up correctly.

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AFTER YOU HAVE PRINTED, CLEAN YOUR SQUEEGEE

(cleaning instructions will be given a different day, before anyone starts printing. But if you're from the future and looking back, read on!)

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Follow instructions given for cleaning (more detailed instructions are found HERE)

You MUST clean your squeegee the same period you use it, so it's available for the next student's use.

You do NOT have to clean your screen right away, as the oil-based ink won't dry, BUT-- you DO need to scrape off the excess/usable ink and put it back in the tub (so it doesn't get gunky from the dust in the air)

And, for this practice exercise, DON'T clean your screen until you've printed the Foil Transfer as well... so that you can practice color-switching without cleaning.

REMINDERS...