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Identifying PCP1 versus PCP2

 
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CAMachin
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PostPosted: Sun Jul 10, 2011 5:53 pm    Post subject: Identifying PCP1 versus PCP2 Reply with quote

I always seemed challenged when identifying PCP1 and PCP2. The Deegam Guide states that PCP1 is typically dull paper while PCP2 is usually glossy with variations in between the two. I have found over time that PCP1 has a noticeably greater after glow than PCP2 under a short wave. In particular I have looked at several copies to include the 17 1/2p, 18p, 19p, and 20p versions. Others seem to follow the same characteristics.

So, I guess what I am trying to determine, has anyone else used this method or am I all wet and it is just a coincidence?
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Gooner
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PostPosted: Mon Jul 11, 2011 1:18 pm    Post subject: Reply with quote

I would be very interested to hear other member's thoughts on this as I have always used the Deegam guide method in the past with mixed results even with known types.
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CAMachin
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PostPosted: Mon Jul 11, 2011 2:33 pm    Post subject: Reply with quote

I received these suggestions from Denis Stevens:

PPP, PCP or PCP1 - Hold stamp at eye level and the stamp will appear to have a matt surface.

PCP2 - Hold stamp at eye level and the head will have a photo negative appearance.

PCP2 (Glazed) - Hold the stamp at eye level and the stamp will be shiny with no photo negative effect to the head.



It is not reliable to check the stamps under the lamp so hope the above helps you.
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tangles2010
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PostPosted: Tue Jul 12, 2011 6:11 am    Post subject: Reply with quote

I'd be keen to know more about the 'photo negative appearance'. I've read that advice before as well, and following it checked some of my Reader's Digest coils for the rare PCP2 version. The trouble is, it seemed to me that all my copies of the second coil were PCP2 - which probably means none are!

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Daniel
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crazyh1
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PostPosted: Tue Jul 12, 2011 9:23 pm    Post subject: Reply with quote

The Deegam handbook deals with this in chapter 6 (page 8 of the 4th edition). Doug highlights that the photo negative effect is not in fact a method to identify PCP2.

In my experience, the most certain identifier is the apparent shade of the stamp in a good light. PCP2 generally has a depth of character to the shade. On the 25p for example, I would go as far as to say its rather fruity (if that's a way of describing a stamp!!). PCP2 colours are livelier than the rather dull mat appearance of the PCP1 sibling of the same basic value. They are also often more glossy in appearance, and that is most easily seen by holding the stamp up at an angle.

I haven't compared the afterglow on them before, but am about to go and do a few to see. I will report back later.......

cheers
Scott
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crazyh1
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PostPosted: Tue Jul 12, 2011 9:44 pm    Post subject: Reply with quote

....I have now done some comparisons on my own material.

In some cases the PCP1 did have a much stronger afterglow, but I have definate PCP2s that match the level of afterglow of their PCP1 brethren (151/2p most notably). Its been a while since I'd looked closely at these particular issues, but on re-looking and upon reflection, I think that perhaps the afterglow could be used as a guide, but not in isolation; especially remembering that storage conditions over the stamp's life can affect the phosphor reaction. The same 'guide' status goes for the photo negative effect. I rather think the latter is actually a side effect of the glossiness of PCP2 paper rather than a feature in its own right and thus is very variable depending upon where on the spectrum from PCP1 to PCP2 any given item lies.

that's my two penneth anyway.

cheers
Scott
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cdj1122
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PostPosted: Thu Jul 14, 2011 1:48 am    Post subject: Reply with quote

I am away at a son's wedding and do not have my Deegam's with me however either in the text of the handbook or one of the "Updates" Doug explains that coil strips exist where one or two stamps appear to have the photo negative effect while the rest of the stamps in the coils strip do not. Or vice versa.

It does not seem possible that PCP I sheets from which the coils were cut had a column of PCP II stamps. Again; or vice versa.
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Gooner
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PostPosted: Tue Aug 23, 2011 10:02 pm    Post subject: Reply with quote

I have just done some comparisons on the 29p Ochre Brown (U312).

TESTS UNDER SHORTWAVE UV

Apart from the level of afterglow I have noticed that the head is noticeably lighter on the PCP1.

NOTE: There is a level of afterglow on two of the PCP1s one is it is much less than the PCP2 version whilst the other seems to be of a similar level.

The Gum however seems to be be duller (almost yellowy) on the PCP2 version.

TESTS UNDER LONGWAVE UV

The stamp that I had already established as PCP2 looks much "glossier" under this lamp. Other than that I couldn't spot any differences.
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Gooner
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PostPosted: Mon Nov 07, 2011 1:15 am    Post subject: Reply with quote

I have been trying to identify the difference in the 16p Pale Chestnut (U244) issue.

To clarify there are three types:
    PCP1 Kampf (DG 165.1.1.)
    PCP2 Kampf (DG 165.1.2)
    PCP1 APS (DG165.1.3)

It is easy enough to identify the APS version due to the irregular perforating, however I a struggling on finding the difference between the two Kampf versions.

I have made a finding though.
Under either longwave or (better) shortwave UV, there is a distinct difference in the gum colour.
One appears much whiter than the other, the second could almost be called grey.
Apart from this the PCP1 vs PCP2 tests in posts above don't appear to be conclusive.

The APS by the way which is definitely PCP1 has the grey coloured gum.

Using the APS grey coloured gum as the principal, I am left thinking that PCP1 Kampf will also be grey which leaves the white gum versions as PCP2 Kampf.

Is there an expert out there who can verify my findings or in fact negate them?
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cdj1122
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PostPosted: Mon Nov 07, 2011 6:36 pm    Post subject: Reply with quote

As I understand it, the quantification PCP I and PCP II is a matter of the apparent glossiness of the printing and not determined by the gum color. It may be that for a low quantity printing such as the 16p the color of the gum might happen to coincide with the different categories of PCP.
However, even so, I don't think gum color could be used across the board on other PCP I/PCP II varieties.
And of course gum color is a useless category to those who prefer postally used examples to play with.
I am also reminded that some time ago I read that the range of glossiness ran from very glossy, through several degrees of glossiness and dullness to very dull. If my memory is right, and I'll check the Deegam later for the exact explanation, what we call PCP I is simply the very dull version of the extremes and the PCP II is at the opposite far edge of being glossy, and thus somewhat subjective.
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Gooner
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PostPosted: Mon Nov 07, 2011 8:30 pm    Post subject: Reply with quote

cdj1122 wrote:
As I understand it, the quantification PCP I and PCP II is a matter of the apparent glossiness of the printing and not determined by the gum color. It may be that for a low quantity printing such as the 16p the color of the gum might happen to coincide with the different categories of PCP..

Well yes and no - They are definitely "different" papers and and printed at different dates and therefore it is not unfair to think that the gum has altered also. * - see below
cdj1122 wrote:
However, even so, I don't think gum color could be used across the board on other PCP I/PCP II varieties.

Absolutely agree and I apologise if that is how the message comes across - I am only concerned with the 16p and if anyone else who has studied this issue can confirm my findings.
I haven't yet found any solution to identification that suits all values so it may be necessary to try and find unique attributes for each value. They may of course not exist.
cdj1122 wrote:
And of course gum color is a useless category to those who prefer postally used examples to play with.

I have enough problems with MNH .. I would have thought that trying to differentiate papers for used versions would be a nightmare considering the process every envelope goes through, the amount of handling, the differing temperatures and weather considerations etc, etc.

The point I make about different papers above has set me thinking.
Deegam lists two (start) dates for this:
    PCP1 January '82
    PCP2 February '82.

Does anyone have a list of printing dates of the 16p (if such a thing exists) or is a sheet printing date a relatively modern phenomenon?

Would PCP1 have been reprinted after the use of PCP2 has started.
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cdj1122
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PostPosted: Tue Nov 08, 2011 2:19 am    Post subject: Reply with quote

The vexatious PCP I/ PCP II issues.

There will be continued confusion for some time as some sources have misunderstood the differences and causes which in today's cyber information age mistakes have an internet immortality of their owm.

Complete Deegam; Ch 6, p8

In 1980 a press notice stated that;
Quote:
" Some recently printed postage stamps have a markedly glossier finish than usual although identical materials have been used in their production. This superficial difference, at present unavoidable, is caused by a complex interaction during the phosphor coating process. The coating process is used because it is cheaper and more effective than the alternative method of applying phosphor during the actual printing of the stamps. Stamps are treated with phosphor so that letters can be franked and sorted by modern machinery. The glossy finish does not affect this. In the interest of collectors, the Post Office intends to eliminate this variation as soon as possible. ".

Furthermore;
" ...... the extremes of range came to be known to collectors as PCP I (dull) and PCP II (very glossy). For many values there are intermediate degrees of glossiness in a continuous range; others exist in only one state or the other. It must be stressed that such varieties do not stem from differences in the mix."
It then goes on to explain that the "photo negative" effect is not a valid test, despite the numerious sources that claim that it is.

And further along Doug explains that such variations are minor varieties at level three with a lower case letter designation unless there are other differentiations available.

Since the Post Office bulletin states; " ... the Post Office intends to eliminate this variation as soon as possible. ..." I assume, from the grammar of the notice, that they are referring to the "glossy finish" on PCP II so that once that was accomplished only PCP I would be produced. It would take some time to comb the listings to discover the dates that PCP I was resumed on particular stamp issues.

Somewhere in my notes there is the blanket statement that " the difference between PCP1 and PCP2 is a matter of glossiness, not phosphor reaction. " And if it is, as noted created during the the phosphor coating process it cannot be a function of the gum either, although it might be a coincidental result in the 16 issue since its limited production was only from February 1982 to July of 1983. Someone with many diverse examples of the 16p might make a table showing the percntage of PCP Is and PCP IIs as a function of gum color.
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Alex
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PostPosted: Tue Nov 08, 2011 9:27 pm    Post subject: Reply with quote

I struggled with this earlier as well. I resorted to buying examples of the PCP1 & 2 types and also found that the PCP2 gum was much whiter, especially under UV light. Earlier comment throws doubt on the photo-negative PCP2 image, or glossy surface, but I have noticed this clear difference on other PCP1/2 types................the discussion continues.....
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cdj1122
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PostPosted: Wed Nov 09, 2011 12:17 am    Post subject: Reply with quote

" ...but I have noticed this clear difference on other PCP1/2 types ..."
I know you are going to throw an old shoe at me, but which clear difference, the gum color or the photo negative effect ?

Sometimes I read the posts and am not certain what is actually meant.
Make the shoe at least a size thirteen so I can get some use out of it.

I am absolutely certain that this PCP I & II business has left other collectors high and dry.
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Alex
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PostPosted: Wed Nov 09, 2011 11:06 pm    Post subject: Reply with quote

Charlie,

I was referring to the photo-negative and glossy effects mentioned earlier.

Alex.
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Wittybebop
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PostPosted: Tue Jun 05, 2012 9:08 pm    Post subject: Reply with quote

I have just checked some stamps which were PCP1 and PCP2 here are my findings.

5p Pale Lilac PCP2 Gum was whiter and has some albeit very short glow in the gummed side, on the stamp surface Short afterglow approx 2 seconds with light held directly on stamp.

19 1/2p Olive Grey PCP1 Gum was yellower and has some albeit very short glow in the gummed side, on the stamp surface Long afterglow approx 5 - 6 seconds with light held directly on stamp.

On comparison these were both cylinder blocks and with the unprinted paper edges side by side and the lamp held approx 6 inches away PCP2 does not glow where PCP1 is quite apparent with afterglow at this distance NOTE This is in a completely dark room and the UV switched completely off.
Also when compared paper to paper in the blocks PCP2 is glossier, but on single stamps I would struggle to see a great differance.

Furthermore I have a 13 1/2p Cyl 1 and is PCP1 as a definate comparison and gives the same result as the 19 1/2p more so is the distance test from 6 inches away PCP2 is virtually non active where PCP1 is very active.
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Gooner
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PostPosted: Fri Oct 30, 2015 12:23 pm    Post subject: Reply with quote

Just re-looking at this posting which is one of the more detailed and gained traction with a few members but I am still not 100% sure that I understood it all.

However (*and in the process bumping this thread to the top of the list).

Can I ask does anyone have a definitive list of stamps issued with the PCP2 variant as well as PCP1?
I thought there used to be a list on the Adminware page but if so it has been taken down.
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crazyh1
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PostPosted: Fri Oct 30, 2015 2:35 pm    Post subject: Reply with quote

Hi Dave,

PCP2 exists on:

1/2p ex sheets
1/2p ex RD coil (I have one of these in a coil strip, so it does exist)
1p ex sheets
2p ex sheets
2 1/2p ex sheets
3p ex sheets
4p ex RD coil
5p ex sheets
12p ex sheets
14p (steel blue) ex sheets
14p (steel blue) ex booklet
15p (ultramarine) ex sheets
15 1/2p p ex sheets
15 1/2p ex booklet
16 1/2p ex sheets
17p (green) ex sheets
17 1/2p ex sheets
18p violet ex sheets
19 1/2p ex sheets (not all agree this is true PCP2)
20p ex sheets
22p ex sheets
25p ex sheets
26p ex sheets
29p ex sheets

The 3 1/2p & 23p are listed in various places, but I'm far from convinced that they exist.....I've never seen one and I've yet to met anyone who has!

The key with these is to remember that they weren't deliberately issued this way, they are a happenstance of production for a shortish period. Hence there is a spectrum with PCP1 at one end and strong PCP2 at the other. PCP2 always has a deeper/richer colour than the PCP1 stamp and the inked area is usually markedly glossy in appearance, its this latter feature that causes the photo negative impression.

The photo negative effect on its own is misleading as other stamps could be interpreted to show it, but those others don't have that glossy inked area. This is most clearly demonstrated by the Readers Digest coil. Deegam makes reference to the issue of the 4p appearing with photo negative and the 1/2p not. That is absolutely true of most of these coil strips, but the true PCP2 version also exists and is differentiated by the more general glossiness.

As previously discussed, there may be other factors that offer a 'tends to' sign. But if you put a page of mixed up PCP1 and PCP2 stamps in front of me, I'd reckon I could pull out 95% of the PCP2s just by the look of them, the colour is so much richer.

Hope that helps
Scott
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cdj1122
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PostPosted: Fri Oct 30, 2015 5:31 pm    Post subject: Reply with quote

Ahm good, Scott posted a list while I have been stumbling about looking for a copy of something I posted in the past.

**********************

The vexatious PCP I/ PCP II issues.
There will be continued confusion for some time as many sources have misunderstood the differences and causes and in today's information age mistakes have an internet immortality of their own.

Complete Deegam; Ch 6, p8
In 1980 a press notice stated that; " Some recently printed postage stamps have a markedly glossier finish than usual although identical materials have been used in their production. This superficial difference, at present unavoidable, is caused by a complex interaction during the phosphor coating process. The coating process is used because it is cheaper and more effective than the alternative method of applying phosphor during the actual printing of the stamps. Stamps are treated with phosphor so that letters can be franked and sorted by modern machinery. The glossy finish does not affect this. In the interest of collectors, the Post Office intends to eliminate this variation as soon as possible. ".

" ...... the extremes of range came to be known to collectors as PCP I (dull) and PCP II (very glossy). For many values there are intermediate degrees of glossiness in a continuous range; others exist in only one state or the other. It must be stressed that such varieties do not stem from differences in the mix."
It then goes on to explain that the "photo negative effect is not a valid test, despite the numerous sources that claim that they can.

And further along Doug explains that such variations are minor varieties at level three with a lower case letter designation unless there are other differentiations available.

Since the Post Office bulletin states; " ... the Post Office intends to eliminate this variation as soon as possible. ..." I assume, from the grammar of the notice, that they are referring to the "glossy finish" on PCP II so that once that was accomplished only PCP I would be produced. It would take some time to comb the listings to discover the dates that PCP I was resumed on particular stamp issues.

Somewhere in my notes there is the blanket statement that " the difference between PCP1 and PCP2 is a matter of glossiness, not phosphor reaction. " And if it is, as noted created during the phosphor coating process it cannot be a function of the gum although it might be a coincidental result in the 16 issue since its limited production was only from February 1982 to July of 1983.
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crazyh1
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PostPosted: Fri Oct 30, 2015 7:12 pm    Post subject: Reply with quote

Charlie,

I had to comment on your point "... and in today's information age mistakes have an internet immortality of their own" - this is absolutely correct, but is valid even before the internet existed. My other area is GB Victorian 1d stars and the standard text books on the topic were mostly written pre 1960....and made statements about official experiments being carried out. This became fact and SG include it to this day, but it is rubbish. Recent research has proven that no such experiments took place and in fact the previous 'truth' was speculation couched in fact which the philatelic community took as real fact because of who wrote it. There is a movement to get SG to rewrite the whole section of their catalogue (which is like moving a mountain when its big changes).

It's important to challenge established knowledge and to apply some scientific rigour to the review. PCP2 is a real thing, but its a production methodology manifestation rather than an intentionally issued stamp. The same goes for the majority of varieties - Machins are a wonderful piece of technology as were the 1d reds.

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PostPosted: Sat Oct 31, 2015 11:18 am    Post subject: Reply with quote

A very interesting discussion, far more so than I had with the Mormons who called at my door this morning with a a pamphlet entitled "Is Religion Dying?"

I won't say where this discussion led as that is for another forum, but it certainly got the old brainwaves tingling early on a Saturday morning.

Thanks for the list Scott - EXACTLY what I was looking for.
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PostPosted: Tue Nov 10, 2015 1:14 am    Post subject: Reply with quote

Taking this a step further and in the process making it worthwhile to have a comprehensive test.
If you go back to my 2nd posting where I discuss the APS/Kampf difference on the 16p Pale Chestnut there isn't a huge difference in the value of the stamp so less reason to be exhaustive in testing,

HOWEVER

I have just come across a value - the 25p Lilac (U288) that has EXACTLY the same issues as the 16p but the difference in retail value could be as much as 100 IF .. you can find a PCP1 Kampf version. My tests to date show the Gum colours to be the same as the 16p versions.

So if anyone feels like going through their (mint) 25p and coming up with a quantitative analysis please let me know the results! I will be doing a bit of checking myself when I get back from my Golf game tomorrow afternoon.
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crazyh1
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PostPosted: Tue Nov 10, 2015 2:49 pm    Post subject: Reply with quote

Dave,

you would also need to do the same test on a control group of stamps that only exist in one or other form, but the problem you will have is that there isn't consistency in the appearance of the gum on any of these. The precise gum colouration wasn't as stringent as the colour of the stamps themselves, and even that shows variation.

I come back to my point, which is essentially the same as that in Deegam (C6-Cool. There is no difference in the materials used in what resulted in what we call PCP1 and PCP2. The PCP2 variant is entirely a creation of the interaction of production processes in just the right mix. It wasn't intentional.

The 25p stamp you refer to is a scarce one, but the 25p is also a good example of the apparent ink colour difference I have referred to previously. If you look at a PCP2 25p it stands out like a sore thumb alongside a PCP1. Other values don't have this extremity. The 16 1/2p happens to be one of the latter, as does the 19 1/2p for example. You can still see a difference though, but the error rate in picking them out on colour increases becasue they aren't as far off to the PCP2 end of the spectrum as the 25p, or 22p.

Scott
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PostPosted: Tue Nov 10, 2015 2:50 pm    Post subject: Reply with quote

that last message seems to have converted a chapter/page to an emoji!

C6 - 8 is what it should have been.
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PostPosted: Tue Nov 10, 2015 5:03 pm    Post subject: Reply with quote

Ah ok .. I understand Scott .. thanks.

I hadn't realised there would be gum variations.
I thought the rules would be stringent but that certainly explains the variety of gum colours over these few years when PCP2 was around.
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PostPosted: Tue Nov 10, 2015 6:35 pm    Post subject: Reply with quote

If you compare gum colours within a type, PVAD for example, then you will see a lot of variation, not as much as for the earlier types typically (ie. GA, PVA), but still a variable. The same goes for lighting the gum with UV, you get some wild variation in that, but collectors haven't picked that up as a type. Probably as it is so inconsistent and insanity that way leads.

Its also important to remember the passage of time. For example, the brightness under SW UV of FCP as compared to OCP will naturally decline with exposure to daylight and any number of other environmental factors. Same goes for practically every feature with the possible exception of the perfs! I have some nice examples of booklet panes which can only exist as FCP which react more dimly than OCP.

I'm a great believer in understanding the manufacturing and environmental processes at work which lead to the stamps we decide are collectible. I fear too many folk collect by the book, with the assumption that if its in the SG catalogue then that's gospel. I'm not knocking anyone's choice here and so no insult intended, but the reality is that SG (and others) have a habit of listing myth alongside truth.....see my previous post about the Victorian period. The more we understand the production and science, the more equipped we are to study the stamps and not rely on those dubious pieces of information. Douglas Myall has done a great service in trying to make the study empirical, but even he would agree that a reflection on previous assessments is healthy. Hence around the loop comes PCP2 and the photo-negative effect Smile
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PostPosted: Wed Nov 11, 2015 11:48 am    Post subject: Reply with quote

" .... seems to have converted a chapter/page to an emoji! ...."

And I thought you ere winking at me !

RE: PCP2
I simply assemble a group and put the more matt on the left, the shiny, or hopefully, the glossy on the right and the most glossy is PCP2. If I later find an example more glossy, it becomes PCP2 and the previous winner of the Glossy Derby becomes PCP or PCP, depending on my mood.
It's 5:30 am here and after five cups of coffee my mood is groggy.

As for SG's listings, I'm shocked, shocked, I tell you.
Happy Veteran's Day.
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Wittybebop
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PostPosted: Thu Aug 25, 2016 9:20 pm    Post subject: PCP1 vs PCP2 Reply with quote

Hi again all, just an update.
I'm currently going through a few dozen cylinder blocks I have, and came across a set of 2 1/2p 25 dot and 25 no dot already set out in PCP1 and PCP2.
So I thought i would have another go at cracking it, all seem to have the photo negative effect which according to, and quite rightly is true (Thanks Doug), that this method cannot be relied on.
Under SW UV, and all white margins being shown next to each other the papers do differ in brightness however PCP1 glows for approx 3 seconds and PCP glows for approx 6 seconds after the UV has been switched off.
Due to previous other cylinders attempts some glow a lot less.
I have alas come to the conclusion that due to different paper colours and different lengths of afterglow it can be nigh on impossible to correctly identify individual stamps and even with cylinder blocks it's not feasible to compare one known PCP type value against another.
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phos45
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PostPosted: Mon Aug 29, 2016 6:13 pm    Post subject: Reply with quote

rather than verbalise , capture UV reactions ...

http://www.ebay.ca/sch/Publications-Supplies/83274/m.html?item=182117701169&hash=item2a670f9631%3Ag%3AvfEAAMXQLoZR01~5%5B%2Fimg%5D&_ssn=cbenbow
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vikingman
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PostPosted: Tue Feb 07, 2017 4:05 pm    Post subject: Reply with quote

Hi
I came across a nice used 4p PCP2 from RD Coil in kiloware sometime ago, it stuck out like a sore thumb and looks completely different from other PCP2 issues. Having since bought the RD Coil in mint condition I was interested to find the p did not have the same effect.

Amongst my many thousands of used issues I have come across an X844 1p and an X855 3p 2 Bands and these have a glazed PCP2 effect, can anyone shed any light on this?
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phos45
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PostPosted: Tue Feb 07, 2017 6:41 pm    Post subject: Reply with quote

I suggest you review stevens lists for 4p and 1/2p coils

http://www.machin-and-wilding-stamps.co.uk/contents/en-uk/d790.html#p2894
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Rein
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PostPosted: Thu Mar 02, 2017 9:06 am    Post subject: Reply with quote

crazyh1 wrote:
If you compare gum colours within a type, PVAD for example, then you will see a lot of variation, not as much as for the earlier types typically (ie. GA, PVA), but still a variable. The same goes for lighting the gum with UV, you get some wild variation in that, but collectors haven't picked that up as a type. Probably as it is so inconsistent and insanity that way leads.

Its also important to remember the passage of time. For example, the brightness under SW UV of FCP as compared to OCP will naturally decline with exposure to daylight and any number of other environmental factors. Same goes for practically every feature with the possible exception of the perfs! I have some nice examples of booklet panes which can only exist as FCP which react more dimly than OCP.

I'm a great believer in understanding the manufacturing and environmental processes at work which lead to the stamps we decide are collectible. I fear too many folk collect by the book, with the assumption that if its in the SG catalogue then that's gospel. I'm not knocking anyone's choice here and so no insult intended, but the reality is that SG (and others) have a habit of listing myth alongside truth.....see my previous post about the Victorian period. The more we understand the production and science, the more equipped we are to study the stamps and not rely on those dubious pieces of information. Douglas Myall has done a great service in trying to make the study empirical, but even he would agree that a reflection on previous assessments is healthy. Hence around the loop comes PCP2 and the photo-negative effect Smile


WoW!

Something sensible at last!

Yes, even the UV-reactions get affected in the passage of time...

What does NOT get affected is - apart from the perforations - the structure of the paper sieve and probably ther surface structure of the paper both in the front as well as in the back...

http://www.galeoptix.nl/fila/uk/thumbs/be_1977_wimpel_h&s_grooves_101.jpg

This feature - incised lines parallel to the direction of paper is typical for Harrison&Sons paper in a certain period!
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Wittybebop
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PostPosted: Fri Mar 10, 2017 12:10 am    Post subject: PCP potency Reply with quote

Just to make identity of PCP PCP1 and PCP2 a little more interesting Very Happy

The phosphor pigments used in the manufacture of Phosphor coated papers used to be organic thermally crosslinked pigments, but Id envisage the organic part of the compound would be suspect to UV (daylight radiation).

So in a nutshell it changes in time when exposed to daylight, and as mentioned by other posters in the last few posts some that are a known type look to be the same as another type

Shocked
Happy identifying.
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phos45
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PostPosted: Fri Nov 17, 2017 4:44 pm    Post subject: Reply with quote

DEEGAM FBO var of 17p PCP

https://www.facebook.com/photo.php?fbid=10213132704885541&set=pcb.10154891143957097&type=3&theater&ifg=1
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