Curing Plastisol Ink with a Heat Press

Here you can discuss any issues related to working with plastisol screen printing inks. This would include curing, mixing colors, additives, brands, usages and much more.

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tomwalker55
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Joined: Tue Dec 31, 2013 5:44 am

Curing Plastisol Ink with a Heat Press

Post by tomwalker55 »

It took a bit of tinkering, but it is working well. It is less than quick, but good for folks who don't have the cash or space for a conveyor.

I flash well enough to get a solid gel cure for handling. Then, in the press, do NOT just squash the shirt!

Turn the shirt over so heat has to migrate through a layer. That slows it down and makes the process more gentle. (Protect against ink getting on the press just in case.)

Here's the key:

I close the press with no clamping - just barely resting on the back of the shirt. Put a light weight on the press handle if you have to, but *no* pressure. *Any* pressure on the shirt will mess it up.

For my gear, I bake for two full minutes (!) with temp set at 330 - 350 (which is about how accurate my press is) and I go off and do something else, like make another shirt. This temp is same as my transfers, a big reason I have come back to using this setting.

With my gear and settings, this does not 100% cure the shirt, but it comes very close. Your shirt should now be set up like a transfer, with ink that will not squish. If you are NOT getting this result at this point you need to tinker with settings and times.

===> You may be able to speed this up with a higher temp and get a total cure, but I want the next finishing step - I want to press it and I like not having to change my settings for transfers.

I do not press immediately - I let it cool a bit by waving it around in the air. I don't want the ink to be tacky at all.

Now to finish, under a teflon or parchment I press for 15 sec at 350, medium-to-firm pressure. The results seem perfect.

+++

By coming as close as possible to 320 before pressure and starting to press with cool ink, my shirts are withstanding a medium pressure to get to a full cure.

Yes - it is slow, but you can multitask (print or paperwork, etc) during the bake stage.

I have tested in a few washes with perfect results, and I am still washing the test sample every day as harshly as I can.
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Catspit Productions
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Re: Curing with a heat press

Post by Catspit Productions »

Aha!!

Awesome! Thanks so much for posting this.

I love it ;)
Jonathan Monaco
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tomwalker55
Posts: 3
Joined: Tue Dec 31, 2013 5:44 am

Re: Curing Plastisol Ink with a Heat Press

Post by tomwalker55 »

A 'big deal' update to curing with a heat press and flash unit... no conveyor:

I sped things up a *lot* for the Christmas rush by looking at the cheapo flash unit as a resource before the press. The press is still an integral unit but it's now *much* simpler and faster because I put most of the curing at the flash stage.

I did some mods that worked *very* well for this purpose. A word of caution: You are totally on your own if you try your own mods. This stuff works on *my* gear.

The main reason a cheap heating-element type flash unit won't work well for curing is that the temperature is uneven from center to edges by a large margin, more than 100 degrees. If you leave such a unit over a garment for a while, you could literally set fire to the shirt before you cure the edges.

The task, therefore, is to even out the temperature...

The open face of the heating element on mine is simply open to the air with a wire mesh to hold it in place. Since the element covers the whole surface, the center area gets very hot while the edges are much cooler. The air at the center is surrounded (and heat-boosted) by the hot air being produced around the edges, so the center gets a *lot* hotter.

The air around the outer edges will remain much cooler because it is only being 'heat boosted' or 'insulated' by the small area of the center, while the outer edges are simply cold air.

In addition, any air movement effects the edge areas immediately. All the cool air in the room where you print can waft by and cool the edges down drastically. That problem is literally forced to continually happen by convection - the difference in temperature near the unit. (Hot air rises...)

Two mods were used - one for the convective air problem and one for the center heat build up.

First, I built simple 1x3 wood edges and hung them straight down around the edges of the unit. This is *not* a problem even with bare wood on *MY* unit, but I can't say it would be safe on yours. It's no problem on mine because the inner edges of the wood never get close to a Fahrenheit 451 thing, but these edges simply stop most of the convection at the edges of my platen. I leave a very small gap above my garment - just 1/2 inch, maybe less - and have no issues with these framed edges hitting ink.

Once the unit has swung into place with these 'edge guards' there is almost no convection loss at the edges.

This is a huge difference (!) but by itself it is not enough to stop the center area from burning by the time the edge areas would be nearing a cure.

To slow down the center area heating, I used some tied wire to hang a plain white ceramic tile from the center of the wire mesh, covering the 6x6" center of the heating element.

I would *not* use a larger tile because you would be perhaps containing the center area heat inside the unit too much, and I left a little gap between the tile and the element. They are perhaps 1/2 inch apart.

This seems to work safely on my setup, and again, you are 100% on your own concerning the safety of the arrangement with your gear. It works on mine...

I've tested this with a temp gun thermometer and this plus the hanging edge frame limits the difference from center to edges to about 50 degrees. It is not perfect, but it is far, far, far superior to the unit as it is made.

With this rig, I flash cure about 30 seconds (longer than about 35-40 seconds starts to smoke). At this stage the ink is nearly cured - it seems to be very close, with some ink fully cured through.

At this stage, I cover with paper and press - no preheating, no padding - for 20 to 30 seconds. My press stays set at 350 and think I get a solid edge-to-edge 320+ all the way through the ink without getting too hot.

The point of the method is that the flash unit has come so close to a good cure that I can go directly to a full pressure hit - there is no damage to ink edges at all. (If you see edges degrading, you have obviously not got the flash unit process going right yet.)

This has tested out well and allowed me to produce hundreds of shirts (about 1100 this Christmas) without substantial delay and without a conveyor system.

As a side benefit, the ink closes up and smooths out on the surface VERY nicely.

I no longer strike-flash-strike for white on black! I double strike, flash and press and get a nice solid white with a superb smooth surface. No roughness at all!

This method has the superior hand and better ink coverage of a transfer plus all the benefits of standard printing - and none of the shortfalls of transfers.

Unless I get to a high volume situation where a conveyor becomes necessary, I don't think I even *want* a conveyor!
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