Artificial lighting (again again)

[DaveW]

For those that do not know what the designation "K" means on lights, it stands for the Kelvin colour temperature scale used in photography amongst other things where 5000K-6500K represents normal daylight.

http://www.3drender.com/glossary/colortemp.htm

The problem with fluorescent tubes is they are not continuous spectrum (that is unlike daylight do not contain all colours of light to produce white) so that was why Growlux and similar tubes were invented for plants. However many seem to find normal tubes work well enough provided you combine two or more colours of tubes to provide a fuller spectrum. To quote from the following link:-

"FLUORESCENT BULBS produce two to three times more light than incandescent bulbs for the same amount of energy. They are the most inexpensive lights for indoor gardening. The color of light produced is determined by the phosphor coating on the inside of the bulb. Cool white bulbs are a good source of blue and yellow-green light, but are a poor source of red light. They are used for interior lighting in schools and office buildings, and are the most commonly available type of fluorescent bulb. Plants grown under cool white bulbs will be stocky or even slightly stunted. Warm white bulbs emit plenty of orange and red light, but less light in the blue and green spectrum. If you are growing seedlings under 2-bulb fluorescent fixtures, you can usually achieve a good color balance by combining one cool white and one warm white bulb."

Also note light duration. Lights should be on a timer since all plants need a period of dark to simulate the normal day-length in habitat, not 24hr continuous illumination:-

"The Right Duration
No matter what types of plants you are growing indoors, you must be sure to always give them a rest. When it's dark, plants respirate, which is an important part of their growth process. The balance of rest time to active growth time affects many biological processes, including the growth rate, and the setting of buds and fruit.

Botanists usually divide plants into three categories relating to their preferred day length: short-day, long-day or day-neutral. Short-day plants, such as chrysanthemums, kalanchoe, azaleas and begonias, will thrive on less than 12 hours of light per day. In fact, these plants must usually go through a series of even shorter days before they will set buds and flower.

Long-day plants require at least 14 to 18 hours of light each day. Most vegetables and garden flowers are long-day plants, and when they don't receive enough light they get pale and leggy. Day-neutral plants, including foliage plants, geraniums, coleus and African violets, are usually satisfied with 8 to 12 hours of light all year-round."

http://www.gardeners.com/Gardening-Unde ... lt,pg.html

This is an American site but may also help:-

http://www.littlegreenhouse.com/guide3.shtml

DaveW

[AnTTun]

Trevor... Ouchie, whole science about few tubes I can already see faces of sales personel in local stores Not sure most of them will be able to even read what I need. Good thing tho is that website you recommended mentiones Sylvania (manufacturer). I know store that sells their stuff, maybe they can order what I need. In the menatime I'll watch if my plants are happy with cool white or they need some red too

Morgans Beauty.. what kind of tubes you use?

Eh heh DaveW, I wish you came up with this few days ago... It took me quite long to find out what that means. I got curious because 5000 Kelvin (or so) simply seemed 'a bit' too hot for plants Now I know what 'kind of Kelvin' it stands for

P.S. Following Trevor & DaveW I found this:

http://assets.sylvania.com/assets/docum ... 551e6a.pdf

Not explaining everything about plants and (artificial) lights but still gives useful info.

[DaveW]

The Kelvin Scale used for light AnTTun means a theoretical black body radiator if heated to that temperature on the Kelvin scale would emit light of that colour.

We have different concepts of light, thinking normally of blue light being a cold colour and red light warm (usually associated with the sun being out), but the opposite is true using heat generated light. If you heat some iron in a fire it first glows dull red then yellow and eventually virtually white hot. However it then melts before it gets "blue hot". However if you think of high voltage sparks or arc welding the light colour is blue since they are far hotter than the red or white hot iron which is why blue light is a far higher K value on the Kelvin Colour Temperature Scale than red or yellow.

DaveW

[AnTTun]

After reading mentioned article few times I have to correct myself: very useful info. Maybe Sylvania doesn't make too good lamps, but they write very good descriptions.

[jfabiao]

If I may add a bit on the subject, Gro-Lux tubes are excellent for plants since they emit light on both the red and blue ends of the visible light spectrum, emulating the peaks of absorption of chlorophyll. The human eye, on the other hand, is most sensible to the green range and that is why the light from a Gro-Lux tube seems "weak" by comparison.

However, Gro-Lux tubes are an old design and not very efficient. Plus, they are expensive. You would do far better by using new(ish) tubes that put out more light for the same amount of energy consumed. When I had a terrarium to grow orchids I used Phillips tubes of both the "warm-white" and "cool-white" variety. They are identified by a number that relates to their colour-temperature - if I recall correctly, these numbers were "827" for tubes that peaked at around 2700K and "840" for 4000K. I never found tubes "hotter" than 4000K, at the time, but I understand that these days there are a lot of tubes and economy lamps claiming to have a 6500K colour-temperature.

Bottom line: one modern warm-white and one modern cool-white tube will give you approximately the colour spectrum of a Gro-Lux tube and will probably cost you less for the pair than the price of a single Sylvania tube. Electronic ballasts, as mentioned, are a must, anyway, as is probably te replacement of the tubes on a yearly basis. Light output decays significantly with time.

[Morgans Beauty]

i use this: Philips Master TL-D 16W/840 HF Super 80 G13 hope you will get it in your area ;-) and sylvania is in germany a cheap mass product without quality!

[jfabiao]

I wrote "Sylvania" as a means to avoid repeating "Gro-Lux", Michael. Although I know that Sylvania manufactures cheap lights, the Gro-Lux tubes are probably not that cheap in Germany. And if they are, send them over here!!!

(and I remembered that the tubes I used were the "TL-D" type, too)

[AnTTun]

If I got all my recent reading correct, point is that 'cool white' lamps (that I use) miss blue and red part of spectrum. Thats why I thought Sylvania Gro-Lux Wide Spectrum tube cold be what I need as an addition. So far I found only their (possible?) equivalent: Osram Fluora (emits blue & red the most) available at local stores. Of course, they are about 4 times more expensive than cool white And of course, salesmen mostly have no clue what I need The search continues....

[iann]

'cool white' lamps (that I use) miss blue and red part of spectrum. Thats why I thought Sylvania Gro-Lux Wide Spectrum

Cool white tubes work just fine. As do the 6500K tubes. Even the 2700K works OK but plants seem to stretch more. Most specialist tubes, including the Gro Lux wide spectrum, have horrible performance in all sorts of respects, but particularly short lives and drastic loss of output over time. Unless you are in a money no object situation spend the money on more tubes, and possible more electricity, to get more light.

[AnTTun]

I admit that so far I didn't notice any unnatural growth with cool white lamps only. I just thought blue/red lamp could be good addition. One thing I should add tho imho (in my humble opinion.. sorry Bill ) is heat source. I think plants would like more than 20-25 C, fluo lamps simply can't make 'chicken box' warm enough. My opinion is that 25-30 would be better for young plants. Am I right?