Mercury lamp alternative for plant growth

Hello all,

In our department we have a large old mercury lamp which is used to speed up photosynthesis and growth of plants for various experiments.

The rig the bulb is attached too is quite wriggly and the lamp itself gives off a remarkable heat.

Knowing that heat has no direct benefit to the photosynthesis process, does anyone have a suggestion for an alternative?

I would love to be able to replace it with something a lot safer and more efficient. Preferably something that could be left on all day without worrying about the thing falling over or blowing up haha.

I have had a look on places like Ebay for growlights but some of them seem a bit too good to be true price wise, does anyone have a suggestion for specific type/brand of light?

Thank you! <3
 

Nick Mitchener

COMMITTEE
Perhaps you should consider LEDs? If you get the correct temp rating the wavelength will promote growth and the floodlight housing types are expected to be on for extended periods. (they do get hot still) Compared to a replacement Mercury discharge lamp they will seem remarkably cheap, but they are still effective.
 
Probably not effective enough if looking for improvement, but we just use an old fish tank, light designed to be permanently on. Aquarium guys very helpful in sussing out best type of light fitting when last one needed replacing..
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Agree if starting from scratch, would look for LEDs...
 
Thanks all! Great help so far.

I should add that we don't do that seemingly dreaded algal ball experiment (thankfully haha), we use the lamp for accelerating photosynthesis in geraniums for all the kinds of practicals we use those for, so the light source doesn't need to be fixed in a tank or anything and would preferably be just a lamp that can be easily moved between the classes.

I'll have a look at LED bulbs of the right wavelength and maybe try and save a bit of cash by bashing something together myself.
 
Thanks all! Great help so far.

I should add that we don't do that seemingly dreaded algal ball experiment (thankfully haha), we use the lamp for accelerating photosynthesis in geraniums for all the kinds of practicals we use those for, so the light source doesn't need to be fixed in a tank or anything and would preferably be just a lamp that can be easily moved between the classes.

I'll have a look at LED bulbs of the right wavelength and maybe try and save a bit of cash by bashing something together myself.
Be careful with grow lights as they only give out wave lengths of light (only red and blue LEDs) best for photosynthesis so can't be used to test wave length and also shine with a bright lilac colour - some do full range though with a few white LEDSs.
 

Nick Mitchener

COMMITTEE
Cree do white LEDs for plant growth. Anything up around 6000 deg K should be ok. When purchasing what is essentially a floodlight you won't know who made the LED but you should be able to get a temperature.
 
Cree do white LEDs for plant growth. Anything up around 6000 deg K should be ok. When purchasing what is essentially a floodlight you won't know who made the LED but you should be able to get a temperature.
It's not the temperature you want for photosynthesis - if fact the less heat the better - it is the light intensity you want best measured in LUMEN (most LEDs show the lumen - get the one with the highest).

There are two versions of LED grow lights - 'warm' or 'cool' (nothing to do with temperature) this is the width of the wave lengths emitted - warm has a broader range so looks a bit more yellow (hence warm) the cool is more blue in colour.
 

Nick Mitchener

COMMITTEE
It's not the temperature you want for photosynthesis - if fact the less heat the better - it is the light intensity you want best measured in LUMEN (most LEDs show the lumen - get the one with the highest).

There are two versions of LED grow lights - 'warm' or 'cool' (nothing to do with temperature) this is the width of the wave lengths emitted - warm has a broader range so looks a bit more yellow (hence warm) the cool is more blue in colour.
The temperature in Kelvin refers to the colour. It is the way fluorescent tubes were rated and has been continued to LEDs. (really the clue should have been in the value)

Floodlights are usually measured in Watts rather than Lumen, and something in the 10 or 20 watt range should suffice.
 
The temperature in Kelvin refers to the colour. It is the way fluorescent tubes were rated and has been continued to LEDs. (really the clue should have been in the value)

Floodlights are usually measured in Watts rather than Lumen, and something in the 10 or 20 watt range should suffice.

I'm glad you've posted this as I had a look again at 'Grow light' LEDs specifically designed for optimum photosynthesis, which is what this thread is about. I knew that LED technology was evolving rapidly and I've noticed that that they are using Watts as a measure (used to be both and some still show lumens) - but this is misleading as it depends on the type of LED in the system and how efficient they are at converting electrical energy into useable light - the new LEDs are far more efficient than the old ones. I will still use the lumen measure as my primary indicator of brightness rather than power consumption.
 

Nick Mitchener

COMMITTEE
You don't need to buy special grow LEDs though, as it is just down to the wavelengths produced and that can be identified with the Kelvin temperature.

You will find plenty of people doing the photosynthesis practical using LED floodlights sold for security. They are extremely cheap and as long as the rating is 6000-7000 degrees Kelvin and a wattage above 10 you will be fine. We use a special LED but that's because we made the lamps ourselves and did not want the commercially available products, however for the job in hand the LED floodlights are fine if you go for the correct temperature and wattage.
 
Brilliant help everyone, thanks!

Now the next question, does anyone have suggestions of where to buy them? Its quite a rigmarole to get stuff in our school if its not from the usual kind of suppliers.
 
Brilliant help everyone, thanks!

Now the next question, does anyone have suggestions of where to buy them? Its quite a rigmarole to get stuff in our school if its not from the usual kind of suppliers.
Screwfix https://www.screwfix.com/p/stanley-...0v/211fv#product_additional_details_container
If you're using just one and the students are lining their experiments up next to each other
B&Q https://www.diy.com/departments/mains-powered-led-work-light-700lm/3663602705413_BQ.prd
If you want them to have one lamp each
 
So it turns out that heat IS an important factor for these experiments so I think i'll have to stick with the big scary lamp for now haha
 
So it turns out that heat IS an important factor for these experiments so I think i'll have to stick with the big scary lamp for now haha
Hope you're really joking - If you use the big scary lamp you will have to put a water barrier up between the lamp and the plants to prevent them from getting frazzled due to the heat produced - that's why LEDs are so good they produce very little heat (comparatively).

In the old days, even with a 60W desk lamp, we had to put a beaker of cold water between the plant and the lamp to absorb the heat.
 
Brilliant help everyone, thanks!

Now the next question, does anyone have suggestions of where to buy them? Its quite a rigmarole to get stuff in our school if its not from the usual kind of suppliers.
The bulbs I use for Photosynthesis experiments are from ESPO, They are MEGAMAN LED classic 1055 lumens (11w) 2800K warm white. These are available in large Edison screw (ES) and LBC. I use them with standard desk lamps, they give out lots of light without the heat and I use them with the Algae and also with pondweed. You can also get similar from Wilko and B&Q.
 
Hope you're really joking - If you use the big scary lamp you will have to put a water barrier up between the lamp and the plants to prevent them from getting frazzled due to the heat produced - that's why LEDs are so good they produce very little heat (comparatively).

In the old days, even with a 60W desk lamp, we had to put a beaker of cold water between the plant and the lamp to absorb the heat.
Its what I've been told by my head of department. They said that the heat was important because during the winter the greenhouse gets very cold. I'm not sure though, as I know from seeing it myself that this lamp can scorch plants if left on for more than an hour.
 
Its what I've been told by my head of department. They said that the heat was important because during the winter the greenhouse gets very cold. I'm not sure though, as I know from seeing it myself that this lamp can scorch plants if left on for more than an hour.
Well I don't think that is wise, it may pose a fire risk and dred to think the cost of electricity! If its greenhouse heat you need, get those tubes fitted they keep the frost off and ours keep it at a temperature of about 10C. you could then use normal LED lamps for the light.
 
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