Quiz..how Does Colour Affect Donuts.

Here is an interesting find that will be curious to some stamp experts out there..

I took 73 Scott 981 "world university games" stamps and captured ALL donuts with this stamp..Below is a diagram of how many donuts appeared on which colours..I was surprised, I thought the donuts would be evenly distributed over all colours..SURPRISE..NOT

Scott 981


Types of donuts I have found.


Here are the distribution of donuts over all colours.


Percentages per colour


Here is the quiz.
1-Why, the darker the colour the ink is, the more susceptible they are to donuts.

2-Why the lighter the colour, the less they are affected to donuts.

3-Or is it that the procedure of what colours are printed in what order.

This post was presented because I hear the "cause of donuts", but I was trained by a large communication company on what is called "root cause analysis"..That is what caused the cause of donuts...And does colour have anything to do with it..Chemicals in different inks???..Unfortunately this training drives my head crazy at times..haha

Converted the image to black and white and put them in order of darkness - I think the correlation between darkness and number of donuts disappears. (I assume, for yellow, we should read orange.)

Sorry Ringo..yes...my mistake, orange is correct..Now to why lets say black is overly affected.

Robert

I always thought that, while they may look like a 'donut', those in the print industry called them 'hickeys'. Hickeys root cause can be either process or material related. Process issues include the speed of the press or printing pressure which cause ink transfer issues. Or they can be material related such as ink viscosity, foreign matter/particles which can attract or repel ink.

http://printwiki.org/Hickey

http://offsetpressman.blogspot.com/...on-your.html

Is it possible to create one after production using chemicals or other contaminates?

Don

But, that does not explain why BLACK colours are susceptible to donuts/hickey more that other colours..??

And it cant be a coincidence that BLACK has more that other colours..I will look for another stamp and see if BLACK is the standard for donuts/hickeys.

Robert

Black has a greater number of donuts than other colour because black is used more than any other colour. The colour has absolutely nothing to do with the distribution of donuts.
Donuts are generally caused by dust sticking to the blanket on the litho press. The dust comes from the usual sources of dust in any environment but also from paper cutting and from powder type dryers. The dust particles fall at random on the printing units irrespective of the colour being printed at the time.
GJP

Garfield, I hope you are not just referring to this stamp, because BLACK has the least amount of colour on this stamp, and GRAY is the colour most used...Just saying.



And also from dried ink after long runs, it gets a skin on it..found that out when I was a printer.
Robert