Thursday 25 October 2018

Ultra-violet lamps for detecting phosphor and fluorescence.

A number of people have asked about what lamp to use to detect the phosphor and fluorescent variants on Walsall-printed Machin stamps.

If you can find a Uvitech Micro, then I would recommend that as the one that I have been using, and through which I have taken all the UV stamp photos shown in earlier blogs.  Unfortunately Ramley stopped making those decades ago.  They occasionally crop up on eBay and other sites, and it is possible that you may find one in an old-fashioned stamp shop (where the dealer has stacks of stuff that he has forgotten about), or in local general (house-clearance) auctions.  However, that is very hit and miss.

This is what you would be looking for.  It takes 4 x AA batteries, and was designed when batteries were slightly less 'fat' than they are now!  One terminal for each battery is a metal stud, while the other is a very flexible spring which holds the battery in place, sort of.  But I have noticed auction listings mention corosion, and I have had the same problem, even if the battery is not leaking through storage.  (Always remove the batteries when not in use - this is a precious and valuable tool; if you can find one, look after it!)

The other thing to check is the switch mechanism; this is not a toggle switch, at least not on mine, and works by depressing a copper strip against a terminal.  Again, over time, this gets worn.  My strip is held in place by some self-adhesive sheet edging, being the right size and much easier to use than transparent adhesive tape.

It works reasonably well in daylight, good enough for a quick look at phosphor bands, to look for short bands, etc, or just to check the colour.  This is because it has an aperture through which the eye can see the lit stamp in relative darkness.

But where the phosphor bands are glowing brightly, it is easier to see fluorescence on the iridescent ink or colour ink if you workplace is in total darkness.  With the main room light off, dimming the computer screen and brightening it again generally provides sufficient darkness and light to see the effects (and take photos), and then to select different stamps.

The model was also sold branded as Stanley Gibbons in the UK, and Scott in the USA.

All the photos I have shown are taken with an iPhone, the newer the better although my previous models have produced acceptable results as shown on the blog in past years.  The camera is in one corner, rather than centralised which probably helps.  I'll be happy to add reports of your experiences with other phones or cameras.

Ramley also produced the Uvitech Minor, a smaller mains-operated lamp which, while useful for detecting phosphor band colours (on Wildings especially I understand) does require total darkness.
Both these lamps are short-wave only and use 254nm light wavelength.  This is important.

Because I have no experience of them, so can't tell you more than I can find by research!
Stanley Gibbons sell a dual-wave lamp for £119 which uses short and long-wave light.  This is the one that John Deering uses for his reports in Gibbons Stamp MonthlyThis also has an eye-piece and is battery operated.  However,  SG's website does not indicate the wavelength although it obviously works.  Another user has declared it to be 'temperamental'.  Maybe new batteries are needed!
Update: I have been told by Gibbons that "the spectrum covered is 254 to 390nm which I believe is the longest range covered by any UV lamp on the market."

Gibbons also sell the SAFE Philalux, which incorporates a magnifier and is also a banknote tester.  The lamps are "Shortwave 266nm with phosphor filter (for identifying phosphor bands and 'all over' phosphor on Great Britain stamps) and Longwave UV lamp 365nm (for identifying fluorescent paper, inks, forgeries and repairs)".  I don't know whether this works for the stamps now available.

A portable lamp with the PRINZ branding is also available for less than £15.  This is battery-operated and therefore portable, but is long-wave 366nm, and so not suitable for our current purposes.  PRINZ also have a 254nm short-wave lamp for under £30 which ought to work.  I was shown a PRINZ lamp at a recent stamp club meeting which was useless for identifying the Walsall variants, so I assume it was the long-wave one.  If the short-wave one does the job, it would seem to be the cheapest option on the market at present.   If you look at their full range, they also have separate mains short- and long-wave lamps, and sell replacement bulbs should failure occur.  They also have a selection of lamps with Lindner branding.
Prinz website -

Only the Gibbons dual-wave has the eyepiece and so can be used in daylight, and probably used for taking photos.

I'll be happy to add any feedback and experiences from readers.   Whilst my lamps don't actually have the designation 'Patent Pending', unlike my (grandfather's) original SG Instanta Perforation Gauge, they are very old but they work.  Your reports on more modern equipment will be welcomed by other readers, I'm sure.   Good luck!

UPDATE 14 November.
Richard Moss has sent me a long email about his experimentation with UV lamps. This is an edited version:

I have Four UV Lamps at home, 
- my old Uvitec, my workhorse of the 90's which gave up the ghost 15 years ago, 
- a longwave battery powered Prinz lamp sold about 10 years ago, 
- a short wave 'Money Detector' desk top lamp and 
- my old Long Wave 'Philatell' model bought in 1970 for testing 'Woodfree' Paper on CW stamps and papers on the high value postage dues of the late 60's. This latter item is unquestionably long wave and is incapable of finding the afterglow on violet phosphors.

I had the following results with the 2018 Yellow Fluors:- 
1) Uvitec - obviously no result as it's broken. 
2) The Prinz Longwave - No yellow activation. 
3) The 'Money Detector Short Wave - very poor yellow on stamps but not every time.   
4) The Philatell Long Wave light. I never expected anything from this and only checked with this for 'a bit of fun'. The stamps were in Hawid Strips and the page covered by a Venus Protector but there it was - a really strong glow which would have been good enough to photograph.

A was talking to Jim Bond on Friday afternoon and he has had a similar experience. He has had his best reaction with one of his Long Wave lights.

I think we all know that some lights give different results to others.The message here is clear, different makes of lamps can have different performances.

So, summing up, before going out to buy an expensive short wave lamp to detect 2018 Yellow Fluors you should test the reaction on all your Long Wave UV Lights.

What really surprised me was that this reaction showed through the Hawid strip.  So if you can, test before you buy, with some known different stamps - if you have the dated examples or cylinder positions that would be most useful.

UPDATE 29 November 
Reader DG has sent details of his US-retailed UV lamp, which has both Long Wave and Short Wave lamps.  As he writes, one disadvantage of this is that is mains-powered so no use for shows and fairs.

Now that I have once again, used my UV light to verify a distinct difference in the two printings of the £1.25, I thought that perhaps I should identify the lamp which I have been using with great satisfaction for over 20 years. I have 2 other hand-helds that I admit, do not produce the same results.

  (£1.25 printing 1 & 2)

Made in the US, it is labelled as a RAYTECH ULTRAVIOLET LAMP, Model LS-2, and has 2 distinctly separate lenses.   It is 7½ inches long. 

As you can see from the picture, it has the European Certification [CE] mark, but the only ones I could find on the internet were US-made 115 volt, so no use in the UK.

1 comment:

    I don't suppose the price of this one is within budget???


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