off contact

[gozo]

What is the optimum off contact for printing on vinyl. My hinge clamps are 8mm thick, so I'm wondering if I have to cut a recess to make the screen flush with the table?

[paul204]

Optimum off-contact will ensure your screen snaps off substrate 1.5--3" behind squeegee. Depending on tack of ink, tension of mesh, vacuum, squeegee angle, image etc etc this will change and you'll have to adjust accordingly, so there is no one optimum height.

From my experience, I would say it always falls between 3 and 8mm, so if I were you I would lower the clamps.

[gozo]

Many thanks for your reply,so my best bet is to cut a recess of the thickness of the clamp to get the screen flush with the table.

[Andymac]

You can always shim under the frame on the clamp if you need more lift, you can't shim down.

The least amount of lift is the correct amount. Like Paul says, it varies job by job and screen by screen.

[NeroInferno]

After all these good suggestions I just suggest: focus you on the viscosity of the ink (is too much dense? is too much thin) and find the minimum OK off contact. Be sure the vynil sheets adheres to the table.

Once more: if the mesh isn't good stretched you need a lot of off contact, if it's good streched you need just the necessary oof contact to lift it under the squeegee.

Considering vynil is flat and not so porous, thin the ink but not so much it can make blurred prints! Make the colour unthinned (or at least a very bit thinned, just to mix it), take another can pour a bit of that colour. thin it until you believe it's okay. If you thinned too much the ink you can use the original colour to raise the viscosity. When the print is okay remember the density of the pressure of your spatula with the ink. See the ink when you mix it. Considering you are using solvent based to adhere to the vynil, consider the idea to re-thin a bit that ink when you'll reuse it, because the solvent can be evaporate with the time.

Fabio

ps. more you thin the ink more you need to have a high number of threads. too much thin = ink that "falls" through the mesh!

[gozo]

Thank you Fabio, I understand. But I'll be back with other question tomorrow after I buy the ink.

[Andymac]

if you are using solvent based, get some retarder paste that matches the particular brand/ink series - fine detail without making the ink too runny. Sometimes they call it sharp printing compound, or microprint gel.

[NeroInferno]

Hey Andy,
here in Italy the Kiian sells for some solvent inks a thinner. There are 3 thinners: slow, fast and normal. But this thinner can be also called as a retarter!? Because they call retarder but a thinner should JUST thin the ink but not acts as a retarder. It's liquid.

Thanks.
Fabio

[Andymac]

slow would be retarder.

normal is thinner, fast is probably for use in automatic printing using a dryer

if they are liquid, they are all 'thinners' they make the ink more liquid (reduce viscosity)

retarder paste allows you to retain the thickness or body of the ink, they use it in halftone printing, and for fine detail.

[gozo]

Thanks for all the advise.
My supplier only sells sericol inks, so I will be using the polyplast inks, and they seem to be quite expensive.
The retarder thinner is sold in liquid form, so next question is. Must I use first thinner to reduce the viscosity and then add the retarder thinner, or can I just go with the retarder cancelling the other thinner.