[theory] What makes white ink so hard to print? Part 2

[blue moon]

so the equipment is here, we are getting used to it. No actual testing has begun as the calibration piece is not here yet. . .

I'd like to start moving through some of the details of printability as I see them. As much other stuff posted here, these are just opinions until proven otherwise!!!

So let's start with the TEMPERATURE. What is happening with the ink as it warms up? What is happening at different temperatures?

pierre

[Sbrem]

Do you suspect there would be a perfect temp, or a range of say 5° to 10° on either side of a perfect temp?

Steve

[blue moon]

Do you suspect there would be a perfect temp, or a range of say 5° to 10° on either side of a perfect temp?

Steve

I am pretty sure that the properties change with temperature and that there is a point at which it is performing best (for your press settings). There should also be a window within it acts pretty close to the "best" temp, but how many degrees is the window is beyond me at this point. It is one of the things we will be testing for!

So, going back to the temps, what happens as we go above or below the BEST temp?

pierre

[jsheridan]

From what I recall, all ink is 'tested' in the lab at 70 degrees

[blue moon]

From what I recall, all ink is 'tested' in the lab at 70 degrees

is your ink 70 degrees when you print with it?

pierre

[jsheridan]

From what I recall, all ink is 'tested' in the lab at 70 degrees

is your ink 70 degrees when you print with it?

pierre

I live in CA.. it's 72 and sunny 8 months out of the year.

[blue moon]

From what I recall, all ink is 'tested' in the lab at 70 degrees

is your ink 70 degrees when you print with it?

pierre

I live in CA.. it's 72 and sunny 8 months out of the year.

so the ink is at 72 when you pick up the bucket, right? and how long does it stay at 72?

pierre

[alan802]

My white ink was 88 degrees yesterday when I was test printing a design through a 180/48.  I was printing at 30"/sec with 35 psi.  I will be doing more testing today and I'll do it earlier with cooler ink and I'll let you guys know what type of results I get.  I have about a dozen prints that I've been examining and I can't believe the difference between the prints with 4"/sec and 30"/sec, it's worth it to print fast.  The 15"/sec prints looked good too, but not quite as smooth as the 30'.

I know most people know this but for those guys who haven't heard it mentioned, print white as fast as you can possibly do it.  That goes for every plastisol color as well really, but obviously white is the most important one to focus on in most shops.

[blue moon]

My white ink was 88 degrees yesterday when I was test printing a design through a 180/48.  I was printing at 30"/sec with 35 psi.  I will be doing more testing today and I'll do it earlier with cooler ink and I'll let you guys know what type of results I get.  I have about a dozen prints that I've been examining and I can't believe the difference between the prints with 4"/sec and 30"/sec, it's worth it to print fast.  The 15"/sec prints looked good too, but not quite as smooth as the 30'.

I know most people know this but for those guys who haven't heard it mentioned, print white as fast as you can possibly do it.  That goes for every plastisol color as well really, but obviously white is the most important one to focus on in most shops.

what do you expect to see with cooler ink?

pierre

[Rob Coleman]

I will throw in my $0.02 here. 

Plastisol viscosity will certainly vary with temperature.  White inks even more so with all the eye of newt and bat wing additives.  An increased viscosity due to cold -s a "false" body.   That is, adding shear (temperature) will bring it back.  Increased viscosity due to higher heat is irreversible -- the pvc resin has begun to swell and absorb the plasticizer. 

Generally speaking, the thinnest the ink will be is around 100-110F.  Ymmv.  Take a look at this rather crude viscosity chart.  Please do not take the numbers as absolutes - they are not.  Merely presented to give a visual image as to what happens when plastiso lis exposed to heat.  The high end 350+ is a remelt.

[tonypep]

Why are you guys still messing around with plastisol

[kirkage]

As the ink warms up, the body becomes thinner allowing you to print on top of the fabric as you need less pressure to clear the mesh

[ABuffington]

Shearing the ink in a turnabout for 10 minutes prior to printing allowed us to use the speed and pressure settings from the night before.  I don't know how a lot of shops in colder climates handle the ink, but we used a combination of heating pads at night underneath the 5 gallon white so it stayed warm overnight and then pulled all ink from the screen in the morning to shear it in the turnabout and this was in Socal with temps at night in the 50's.

[Rob Coleman]

Why are you guys still messing around with plastisol

Nice!   

I know you are talking about hand-feel, cost, fashion, etc.  However, it is only a matter of time, though, for many.   8 of the top 10 global fashion retailers have some sort of PVC restriction in their RSL.

End hijack .... back to your regularly scheduled programming!

[blue moon]

I will throw in my $0.02 here. 

Plastisol viscosity will certainly vary with temperature.  White inks even more so with all the eye of newt and bat wing additives.  An increased viscosity due to cold -s a "false" body.   That is, adding shear (temperature) will bring it back.  Increased viscosity due to higher heat is irreversible -- the pvc resin has begun to swell and absorb the plasticizer. 

Generally speaking, the thinnest the ink will be is around 100-110F.  Ymmv.  Take a look at this rather crude viscosity chart.  Please do not take the numbers as absolutes - they are not.  Merely presented to give a visual image as to what happens when plastiso lis exposed to heat.  The high end 350+ is a remelt.

fantastic graph, I was debating posting one, but did not have and was to lazy to draw it! Thanx Rob!!!

What can we conclude from it? As Rob already said, it will be the thinnest around 100 degrees. Is that what we should be going for? Is the thinnest the best? Why not set up the press for 140 where the ink has more body?

Alan, what temp was the pad set for?

pierre