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Welcome to  ‘Ask The Expert’.  This page is moderated by industry consultant, Steve Wilkinson.  This page features the answers to your questions. Our visitors can also post comments to these questions/answers as well.  You can learn more about Steve’s background and our ‘Ask The Expert’ page by Clicking Here.

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April 21, 2010

Our operators keep losing or breaking the ph meters we provide, so for the last few months we have not replaced them, everything seems ok, or is it?

I assume you are using water soluble inks based on you having been using a ph meter in the past. I truly hope you don’t really think that not having any ph meters can possibly be ok. I am certain that if you talk to your operators or better still look at your print quality you could not fail to hear about or notice variation in your print quality, ink transfer, anilox plugging, color densities..

Proper pH  control although not an issue for UV or solvent based inks and is a measure of the alkalinity or acidity of a liquid and has a scale of 0-14.

Most water based inks function based with a pH  between 8 and 9.5 but as inks are run they get hotter and as a result burn off the ammonia and/or amines in the ink.

This will cause the ink to dry faster and if you try to adjust your viscosity at this point it really would have no effect until you have lifted the pH reading back to between the 8.0 and 9.0 as recommended by your ink supplier.

Clearly you need a good quality pH  meter that must be made available at all times if you are to be able to read the pH and hence control your inks performance and hence quality of your print, and in many other areas as well.

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April 1, 2010

We are offset printers but are being told by many buyers that flexo is simpler, cheaper and can match our quality, I do not agree but have no real flexo experience, so who is right?

Let me first of all say that this is a topic that we may never agree on because it really depends on how open minded we can both be.
As you said you are an offset printer, and I have been involved with flexography all of my working life, and similar to your not having experience with flexo I have to admit to not having spent much time delving into the offset process.
In fact I have spent most of my career defending and lobbying for flexo in the same way as you have for offset.
So now we know where the lines are drawn, let me first try to define the two processes and then begin to make some comparisons before finally trying to answer your question.
Offset uses a surface thin plate that has a surface treatment that attracts ink and water to different areas that are then transferred to a blanket which in turn transfers the imaged areas to the substrate.
Flexo on the other hand uses a rubber or photopolymer raised area that is inked up by an anilox roll before transferring the image to the substrate.
Now I mentioned the word ink, and again this is where the two processes differ dramatically. With offset you have thick oil based slow flowing ink that has to be transferred between a chain of rollers to make it thin enough to transfer to the treated plate surface. With flexo you have a choice of water, solvent and UV liquid inks that flow and dry rapidly.
Now to try to answer your question perhaps I should respond to each of the points that your buyers were saying about flexo firstly being simpler.
As much of an advocate as I am for flexography I have to admit that achieving good, consistent print quality with flexo is anything but simple.
Compared with offset the skilled flexographer has a lot of choices to make such as which ink system, what type of plate, thickness and hardness of plate, what mounting tape to use, to name but a few of the many options that have to be made. So simpler, I would have to disagree with but would have to say that today many flexographic printers follow strict industry guidelines that help make the process very repeatable and consistent.
Again with the second statement of flexo being cheaper I do not believe that this is the right word to use, competitive, good value for your money. Like most buyers that don’t know flexo they equate the first statement of simpler to meaning cheaper when in fact I have already proven that the many options that have to be considered in flexo compared to offset make it anything but simpler, but consistent and highly efficient techniques, processes and equipment in flexography today do make it very competitive.
Now to the quality term and on this point I have to agree there are many areas that flexographic print quality does compare favorably with offset and on some substrates I would have to say does an even better job. The truth is flexo can print on the widest range of substrates of any print process which is one of the major reasons for its popularity in the first place.
So who was right?  Simpler, cheaper, a match for offset quality, it all depends on how much you really understand about each print process, so now that you know a little bit more perhaps you will be able to make your own decision., But if you want more information to make a more educated decision write back to me with more questions or comments and we can continue the debate.

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