The Mystery Of Irish Stamps (Wrong Colour Or What?)

Just to muddy the water even more ... if the paper and yellow color are correct, then it must indicate that the BLACK is incorrect. Therefore it might be an error of design and value. I still think that if that error exists then it must also indicate at least one whole sheet is involved.. i.e. a whole sheet of yellow printed with the wrong black design and value.

Thank you, scotzm, for the idea. I'd wish some people collecting Irish definitives would pass judgement too. I could not find a forum of people collecting Irish stamps though, just occasional discussions unrelated with the subject I am interested in.

You could start a topic with a title ' Irish Definitives ' or something similar and add to it yourself and then others would add to it also, as you did, and it would grow over time perhaps?

Perhaps just changing the title of this thread to include those words would be OK?

Thank you, Puzzler, for the suggestion. I'll definitely do so, especially that I have got some other Irish stamps which can be a subject for discussion.

One more thing I also want to find out. Would the ink of the cancellation change were it exposed to the sun or treated chemically?

The ink of the cancellation will cange to a lighter shade when the stamp is soaked many times in water. Chemicals no doubt could have the same result.

At times chemicals are used to achieve asingle colour change so as Not to change any other colours, to falsify the stamp. Sometimes this is accidentally done also.

I could not rename the topic. Is it technically possible?

When you are signed in and then Edit (icon showing paper and pencil) a reply, the very first one you started the topic off with, then the title is in a line separate above the posting.

Now, thanks to Puzzler, I have renamed the topic and can tackle a few other issues of colour that I have noticed in some Irish stamps.
As an example I am showing two Xmas stamps differing in the background. Anyone with suggestions?
Concerning the initial yellow stamp 28p the question remains, if it is a changling, what caused it without affecting the cancellation. Or was it first changed (what for then), then used.
Constuctive ideas are most welcome.

The cancellation is black. Modern black inks are very stable and do not fade easily. Even so, since we do not know what the cancel looked like originally, we have no way of knowing whether it is changed or not. Also we have no way of knowing when the color change itself occurred, it might have been before the stamp was cancelled.

UV light exposure is one thing that might drive a dye to color change. The sun is a good source for UV light; take a normal orange stamp and mask half of it, place in direct sunlight for a few weeks, remove mask and see if you can detect a color delta between the masked and unmasked sides.

to revcollector
If you look at the photo Posted 09/24/2013 with 13 stamps you will see that all the cancels colours seem to be the same saturation.
to 51studebaker
Will the orange colour turn into yellow ? If so, will any pigments of orange stand any chance of remaining at least partially?

Yes, I would suspect that orange would fade to yellow but this is just my opinion. Placing a few masked stamps on a sunny, south-facing window sill for a few weeks should give you a better understanding if this could occur. The color fastness of the dyes in printing inks (and coatings) is pretty stable for obvious reasons, it might take a few weeks to see a change.

In your image it appears to me that the black ink is also slightly lighter in color compared to the orange stamp. But note that different colors can be more or less susceptible to UV fade.

I would speculate that if the stamp doesn't fade at all after several weeks of direct sun exposure then you could rule out UV exposure as a possible reason for the yellow color of the stamp.

Orange is a combination of red and yellow. Red is one of the more unstable colors and fades fairly easily, so if it did, yellow is what would be left. I still think that the UV reaction points to a chemical alteration rather than sunlight, but either could do it.
I have seen stamps ca. 1950 that were completely bleached by the sun, all color was gone (green in this case) but the black was barely affected.

to 51studebaker
Placing the stamp on a window sill does not help too much in my case: where I live there is little sun, except some summer days. Also I have seen some faded stamps, then the paper itself becomes faded and dull, while this one looks as healthy as the red-orange one.
to revcollector
As you can see in the pictures this orange is much closer to red than actually orange; so simple deduction of a pigment might not be the case.
I wish someone familiar with the printing techniques would give us a idea.