Fluorescein dye

darklord

Member
Can anyone recommend a good supplier/source of liquid fluorescein dye (or perhaps pwder if that is the preferred format these days?
There's a lot of stuff online, but much of it looks like 'drain tester' stuff which I doubt is the real mccoy.
 

Pitlamp

Well-known member
If you know an industrial chemist I believe it's not to difficult for them to home-brew the stuff.
 

Stuart France

Active member
You should buy fluorescein powder, not a solution of it. Make up the solution as needed. Toolstation sells the Screwfix product for £1 less:

A little goes a l-o-n-g way. I bought a 100g BDH bottle of lab-grade material "in the day" and I still have a fair bit left. Just a teaspoonful of fluorescein dissolved in 250ml of water poured into a small surface stream can turn the underground water in a cave hundreds of metres away bright green for a positive connection. See photo. No need to deploy clever sensors or data loggers for short range experiments! Bear in mind where the cave water resurges (or might resurge) to avoid embarrassment. Your local water company would be unamused at finding a fluorescent green reservoir.

There are colourless alternatives, known as Optical Brighteners which are added to washing powder to make your shirts "whiter than white". OBs are invisible to the naked eye, so no risk of creating an embarrassing green slick trundling its way through some nearby village... But you then need either a fluorimeter coupled to a data logger (to detect and record the dye pulse as it passes through the cave) or place swabs of surgical cotton wool (the cotton wool that Boots sell) which are free of OBs at the point of manufacture. The swabs will absorb the dye as it travels through the cave and can be viewed later on under a UV light later to confirm it was there. The most well known material is Tinopal powder, fairly cheap and sold online - dissolve before use. Ebay sells "UV torches" suitable to examine swabs which will fluoresce if they've absorbed the OB dye on its journey.

Yes it is simple to make a crude fluorimeter with just a UV LED pointed at the wet swab and digitise the reflected visible light level in total darkness in-cave then log the reflected light level versus time. Bear in mind that cave water carries other natural dyes, like organic material, aka crud, so your swabs will lose reflectance as time goes by, but when the tinopal comes past there will be a step up in the UV converted to visible light. See chart: the 50g of OB in the chart refers to 50ml of a prepared solution, not the raw powder!!!

Fluorescein and tinopal are reasonably safe since your local hospital would drip the former in your eye to visualize surface damage and everyone's washing machines discharge the latter after whitening/brightening the nation's clothing to some degree.
 

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JonathanV

New member
Always good to let the Environment Agency/Natural Resources Wales, SEPA know in advance so they are prepared for any calls from the public.
 

Stuart France

Active member
I have heard that if you drink some then your pee turns fluorescent green as it is excreted un-metabolised. Could cause a stir in the gents or feminine equivalent. So it's best if you can arrange things to avoid any phone calls from the public about little green men from alien spacecraft etc etc.

I think just 100g of fluorescein powder would do the job if you wanted to reproduce the Canal & River Trust Effect.
 
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mat

Member
I have heard that if you drink some then your pee turns fluorescent green as it is excreted un-metabolised. Could cause a stir in the gents or feminine equivalent. So it's best if you can arrange things to avoid any phone calls from the public about little green men from alien spacecraft etc etc.

I think just 100g of fluorescein powder would do the job if you wanted to reproduce the Canal & River Trust Effect.
I can vouch for this. Decades ago I used to work in a lab and I acquired fluorescein. As a party trick I used to drink it, twas hilarious when going for a leak in pub toilets and people staring, I would tell them I worked at Sellafield. It was like the parting of the Red Sea, folk would move away.
 

alanw

Well-known member
In the late 80's I worked with someone who told this story: he used to be an oceanographer, and Sellafield/Windscale/Calder Hall commissioned him to do a survey of the tides and currents in the Irish Sea. He chartered a fishing boat and set sail with large quantities of fluorescein. They all put on white disposable coveralls before pouring it overboard. When they returned to port (Whitehaven?), glowing green, in a boat known to have been chartered on behalf of the Atomic Energy Authority, it caused a certain amount of consternation.

True or Urban Legend? It's just plausible enough to be true.
 

Graigwen

Active member
It's worth reading Norbert Casteret's books if you want advice on making sure a fluorescein test is definitely positive.
If I remember correctly, you need donkeys and a grandmother. How many kilometres of the Garonne did he turn green?
 

Dave Tyson

Member
I can vouch for this. Decades ago I used to work in a lab and I acquired fluorescein. As a party trick I used to drink it, twas hilarious when going for a leak in pub toilets and people staring,
Methylene Blue also passes through unchanged. A chemistry student's contribution to a bowl of punch at student parties. Makes a nice looking drink and causes amusement when people pee green or blue depending on the volume consumed...
There are also some red dyes whicb pass unchanged, but I think they cause rather more concern!

Dave
 

ChrisB

Active member
In the late 80's I worked with someone who told this story:
In the mid 1980s I actually worked at Sellafield. One of our projects was to test new ways making watertight joints in concrete. The test rig included some concrete with a joint in it and an assemblage of hoses to apply water pressure. We could see that the pressure dropped but not the point where it was leaking from. Fluorescein was added to the water, and pressure re-applied, at which point one of the hose clamps slipped and my colleagues were drenched in green dye, with similar reactions when they went home.
 

wellyjen

Well-known member
In the late 80's I worked with someone who told this story: he used to be an oceanographer, and Sellafield/Windscale/Calder Hall commissioned him to do a survey of the tides and currents in the Irish Sea. He chartered a fishing boat and set sail with large quantities of fluorescein. They all put on white disposable coveralls before pouring it overboard. When they returned to port (Whitehaven?), glowing green, in a boat known to have been chartered on behalf of the Atomic Energy Authority, it caused a certain amount of consternation.

True or Urban Legend? It's just plausible enough to be true.
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darklord

Member
Thanks everyone for all your suggestions....and hilarious stories/anecdotes! - it sure is a substance to be reckoned with!

Stuart France - thanks for the detailed response. I'm quite familiar with using OBA and have done many tests using the cotton wool and UV light method - many of these tests are logged on the The Northern Caves & Karst Hydrology Database . I've just never much used Fluorescein and wanted a 'quick check' method with a party in the other cave as observers - we reckon no more than 20-30mins for water to travel the distance. So maybe just a teaspoon of 'drain tester' from Toolstation will be fine. It's unlikely to be turning the Lune green!
The liquid solution I've used before was deep red in colour, a bit like iodine - but turned green instantly on contact with the stream water. Fluorescein was handwritten on the bottle...but maybe it was Rhodamine...?
 
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