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Silicone coated - how to detect?

 
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Thunderbird1
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PostPosted: Sat Mar 11, 2017 3:15 pm    Post subject: Silicone coated - how to detect? Reply with quote

I'm trying to find out if I have a 1p crimson silicone coated machin (DG 10.1.3) in front of me. I don't have a G1.8 multivalue coil strip which also includes the 5.1.3 and 20.1.3, but just a single.

DG glossary quotes "Because the coating was screened 150 it can be seen in angled light."

I'm presuming that the silicone is printed over the phosphor bands and if these are already 150 screened/printed, would that mean the stamp is 150 screened silicone over 150 screened phosphor? Hmm.. I'm kinda stuck Wink

What's the best way of detecting these apart from the angled light? I can't detect a 150 phosphor from a 250 phosphor without the magnifying glass let alone the naked eye. Will the shortwave uv give a different lighting than the non-silicone DG 10.1.1/2? Any tips/tricks?

TIA, Marc
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crazyh1
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Joined: 20 Nov 2010
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Location: Lincolnshire, UK

PostPosted: Sat Mar 11, 2017 7:33 pm    Post subject: Reply with quote

Hi Marc,

the answer to this depends on how many stamps you've looked at - ie. there is a an element of experience in identifying them.

The Silicon coated exhibit the following features;
1. When held at an angle to the light, the phosphor bands are far less distinct on a silicon coated stamp than a non Silicon coated stamp. The appearance under UV is not usually so different.
2. The colours of the stamps appear more matt, a little muted.
3. The silicon screen can be seen - you need a x10 (or more) magnifier for this. The nest place to look is in the white margins between the phosphor bands. As you infer, seeing one screen on top of another is a bit of a non starter. Sometimes you can make it out over the coloured print, but that itself is screened of course, so can be misleading. Hence, look at the white area. You will need to have a good strong white light with the stamp held at an angle and then when examining, slightly move the stamp around to see if the changing light angle helps you see anything.

As with most varieties, identifying these on used stamps is 100 times more challenging and more prone to error as the stamp will have been exposed to who knows what in its travels.

So, the starting point is to make sure you have a firm idea of how marked the contrast of normal phosphor bands are as compared to the rest of a stamp and then keep that in mind when looking at others. If you have one where the bands are not obvious, you might have a silicon coated stamp and can use the other criteria to confirm it. The silicon screen is not as obvious as Deegam would have you believe.

Handily, the FCP silicon coated stamps are pretty common, so you can hope to pin those down before hunting down the scarce OCP stamps.

Hope that helps.
Scott
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phos45
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Joined: 17 Aug 2007
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PostPosted: Sat Mar 11, 2017 9:05 pm    Post subject: Reply with quote

denis stevens...
OG1RS - 1p crimson, OCP/Arabic, two 4.75mm screen 150 B3 phosphor bands, sideways print right (G1 multi-value coil) (Harrison/photo) - Deegam 10.1.3 - Stoneham M48d
Silicone coated, sideways print right from G1.8 multi-value coil [12.72] Out of stock 30.00 GBP

http://www.machin-and-wilding-stamps.co.uk/contents/en-uk/d668.html

deegam ...
Silicone coating
To prevent stamps on the multivalue G1 and G2 coils (see appendix 1) from sticking to each other, a non-toxic silicone was applied all over them. This short-lived experiment lasted for six months from December 1972. Because the coating was screened 150 it can be seen in angled light.
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Thunderbird1
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PostPosted: Sun Mar 12, 2017 10:31 am    Post subject: Reply with quote

Thanks Scott. I really appreciate your help.

So, I guess what you are saying is that if I look on the white margin between the phosphor bands, I would see the criss-cross grid effect as per the 150 phosphor bands. Is my assumption correct?

I've already checked the dealers for the FCP/GA version which would be DG 10.6.1 or 10.6.2. It seems they only go for a few pence. It does make me wonder as I have seen 'silicone coated' machins go for big bucks on eBay a few times. But maybe that was the OCP version.

TIA, Marc
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crazyh1
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PostPosted: Sun Mar 12, 2017 10:57 am    Post subject: Reply with quote

Marc,

yes, you would (or at least stand a chance) of seeing the grid pattern in the boarders between bands. It is not always that clear, just as is the case with the phosphor screens!

The best starting point is the indistinct bands.....if you see that, then use the other features as confirmation. The books tend to approach it the other way round, but, as you have seen, its not so easy as the books make out.

The FCP ones are indeed cheap as the coil they come from was intentionally silicon coated in an attempt to reduce problems in the vending machines. The trial wasn't as successful as hoped and so only the one coil is affected. The OCP version is rare, only one or two rolls were ever found and it is believed that this was a case of a very small remnant of the OCP paper being used up during the FCP silicon coated trial.

So investing in a strip or two of the FCP silicon coated coil from a reputable source could ultimately pay back if you get a handle on the identification and then later find an OCP coil.

Scott
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crazyh1
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PostPosted: Sun Mar 12, 2017 11:00 am    Post subject: Reply with quote

I should also have said that before anyone parts with bigger money for the OCP version, they sure make sure they know what they are looking at. I have bought OCP strips in the past that claimed to be silicon coated but weren't. Always returned and refunded, so no harm done to me, but for anyone who just trusts that dealers are always right there is a risk.

The well known specialist dealers are usually right and others may well be, but everyone makes mistakes........
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phos45
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PostPosted: Sun Mar 12, 2017 11:23 am    Post subject: brightner omitted Reply with quote

https://stampauctionnetwork.com/RM/535/1221.jpg

MH42avar: 12p multi-value COIL STRIP of four containing one p and three 4p Machins, all with FLUORESCENT BRIGHTENER OMITTED, a pristine strip with full intact original gum and never hinged, very fine and exceedingly rare thus as all but a handful of these strips were affixed by waxed strips to Readers Digest promotional cards. (SG Spec UMC10a - 2000)
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Thunderbird1
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PostPosted: Fri Mar 17, 2017 12:52 pm    Post subject: Reply with quote

Thanks as usual Scott. It's nice to see that someone out there is willing to help.

@phos45 - I don't get what you are trying to tell me or anyone else interested in this topic regarding the identification of silicone coated stamps. What has FBO to do with silicone coated - can you explain? Maybe a couple of written sentences might help this thread instead of pasting snippets.

Thanks
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crazyh1
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PostPosted: Fri Mar 17, 2017 1:58 pm    Post subject: Reply with quote

No problem Marc. I'm always happy to share what I know....I still learn new stuff every day, but no point reinventing the wheel all the time.

I occasionally think about writing some sort of book to offer these notes to the wider community, I've never taken it further than the odd thought as yet though.

Scott
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