[Basile]

Hello guys,
I am new here and new in screen printing as well. I have been trying to print white waterbased ink. First on a red t-shirt without curing. The print washed out. I considered this a failure. Secondly on a black t-shirt which i cured for 3 minutes at 160 Celcius, but the print washed out as well.I must say that i washed both of the t-shirts on 40 Celcius. Later on i cleaned my screen from ink with "extremely" hot water ( i mean it was hot, not just warm), and the emulsion started to wash off.

So i want to ask you two questions if possible.
First, why water based ink washed off even though i cured it? (i didn't use discharge). Is it the temperature of 40 Celcius too high?
And secondly, does the hot water hurt the emulsion and it washed out the screen or something else could be the problem?

Thanks in advance

 

[SlashX]

I'm new to the forum also. I look forward to the answers.

 

[TABOB]

Which water-based ink?
You've just used acrylic without the textile medium haven't you?


Water-based inks do breakdown the emulsion fairly fast.
You can try and post-cure the exposed screen before its first use it. If this does not help, you will have to use an emulsion hardener. Note that you may not be able to reclaim the mesh if you do this.

 

[SlashX]

I was thinking, he's not using a water based emulsion. That might be the issue.

 

[Basile]

@TABOB I am working with Hunt the Moon ink because i don't have a big budget yet and i want just to try the screen printing in the beggining, plus i live in Europe. The emulsion i use is Jacquard's Photo Emulsion with Diazo Sensitizer.
What do you mean with "used acrylic without the textile medium"?
Sorry but i'm not good with terminologies yet.
@SlashX I don't really know if it is waterbased and unfortunately it does not mention it somewhere.

 

[TABOB]

@SlashX
Of course it is water-based emulsion, which one is not?

@Basile Looks like you have screen-printing ink then. Are you sure it reached 160C for 3 minutes? How did you cure it? Heat press, belt dryer, kitchen oven?



Believe me, it is much easier to start screen-printing in Europe than in the US. In some of the countries at least.

 

[sben763]

Almost all diazo emulsion can be used for water base ink but not all. When exposed diazo becomes water resistant. You maybe under exposing therefore a need to post expose to obtain a stronger stencil. A full exposure the first time will create the strongest exposure. A good indication that a screen is under exposed is when you go to reclaim it. If it is tough to reclaim it’s likely under exposed.

Try throwing the exposed screen in the sun for 30-60 min after you wash out. If it’s a sunny day I made a rack and dry all my screens outside after exposed and washed out.

 

[Basile]

@TABOB I cured it in the kitchen oven. I turned it on and let it one minute, then i put the T-shirt in and i waited 3 minutes to pass. (black t-shirt)

I live in Greece so unfortunately many of the Screen Printing supply companies does not ship their products here.

*Note*
I tried to print to light blue coloured t-shirt. I think it's better than the rest of my tries. It seems like ink hold up stronger. I do the stretching test after curing and i washed the t-shirt in 40 Celcius and ink didn't wash out.

 

[Basile]

@sben763 I exposed my screen in the sun for 30-45 seconds. I didn't post cure it. I printed i think about 10 times. After each time i cleaned the screen with a bit of ink remover and water. Then i let it dry before printing again. The last time i printed i cleaned the screen from the ink with extremely hot water and without any ink remover. It was this time the emulsion started to wash off the screen.

Is it true that if the screen is underexposed, it's tougher to reclaim it?
In my mind if the screen is properly exposed is tougher to reclaim it because the emulsion is much more hardened.
I am new so maybe i am wrong, so forgive me

 

[TABOB]

Haha... in the kitchen oven. I knew it.
Well right there is your problem. The 160C is not the ambient temperature. It has to be the temperature of the ink itself for 3 minutes.
For water-based inks you really need a forced air belt dryer, or a heat press with hover functionality (so you can dry and press).


I think sben763 missed a "NOT" his post. The emulsion should be tough to reclaim. However, don't use hot water to wash stencils you plan to re-use, and don't wash for too long.

 

[Basile]

@TABOB Oh i see. So 160 temperature should be aimed on the ink. Thank you man for the advice. One more question, does a heat gun work or i must buy a heat press?

 

[sben763]

Under exposed emulsion can lock or be difficult to reclaim. Properly exposed emulsion actually reclaims very easily.

With water base ink the water has to be removed and then the ink be at curing temp. There are many people that use a heat gun. There are also a few air dry water base but require a catylst.

Please don’t use your oven that one cooks their food to cure shirts. Even waterbase although many companies claim their safe contain some nasty chemicals. They only legal way they are allowed to do so is the amount is lower then need to have warning labels. Look at the MSDS, SDS

 

[TABOB]

OK, what sben763 says about the emulsion, doesn't make sense to me, but I don't use normal emulsion, so maybe he is right.
Heat gun can be used for drying, but it is impossible to maintain even and constant 160C for 3 minutes with it. Newbies usually use a heat-press, or a large flash dryer. If you do this measure the actual temperature reached in the center and the edges with a laser thermometer. Any variation must be small.
As far as I know, catalysts reduce the curing temperature, but still require heat curing.

 

[Basile]

I watched a video from Ryonet for underexposed and overexposed emulsion and if i understood well, underexposed emulsion can lock inside it ink remover, degreaser, and emulsion remover which makes the screen reclaiming harder. So i guess @sben763 is right about the difficulty of screen reclaiming of underexposed emulsion.

Anyway guys, thank you for all the answers i think i'll become better as the time passes. I'll try what you advised me and i hope for the best.

 

[sben763]

With the heat gun curing, you will never get the entire surface to the cure temp. You must though get all areas to your cure temp after all the water has been expelled to set the pigments in the ink.. Its slow and very unproductive. there are several members here that started out with a heat gun or flash unit. I started with a flash unit myself but only printed a few jobs before investing in a conveyor dryer, which if your doing any volume is needed.


There are a few brands of water based ink that you can use a catalyst for the curing. Union Aerotex inks at one time showed complete curing in 12-24 hrs with no heat. I never tried and don't see the option on the instruction sheet with the QT I got today. There is another thread about 7 years ago talking about this and I got samples from a guy(supplier) to compare to the Union those I did do a no cure to and they worked fairly well but had warning of good ventilation as well as a smell after cured similar to discharge printing and why I don't do discharge. Others catalyst simply lower the curing temp as in the case with a nylon catalyst.




To understand the entire process of emulsion one needs a chemistry degree. When you expose a screen the UV light transforms standard polymers to I believe they call they radicals, theses radicals bond and change the solubility to water. When you reclaim the screen the chemicals break the bond and restore the solubility to water. When under exposed the radicals don't fully form and the sensitizer that forms the radicals is still partially sensitive. This allows ink wash, emulsion remover, and other chemicals to make and lock the solubility to water. When reclaiming screens if you ever let the emulsion remover dry it will raise the solubility to water to almost zero permanently locking the screen.

 

[TABOB]

I watched a video from Ryonet for underexposed and overexposed emulsion and if i understood well, underexposed emulsion can lock inside it ink remover, degreaser, and emulsion remover which makes the screen reclaiming harder. So i guess @sben763 is right about the difficulty of screen reclaiming of underexposed emulsion.

This does make sense, and also explains why I never had this problem.