Hydroponics BC


   Types of lights:
Incandescent bulbs, like the one in your bedside lamp create light by passing electrical current through a very fine wire. Resistance in the wire causes it to heat up and glow.

Flourescent tubes and low pressure sodium lamps pass electrical current through gaseous vapour under low pressure. Flourescent tubes are very good for seedling and cuttings. Flourescents can be kept very close to the leaf canopy without fear of scorching. These can be raised as the plants grow. If your plants require medium-high, or high light levels flourescents are not recommended.

Low pressure sodium lamps and mercury vapour lamps are of little value in the case of indoor gardening. Restrict their use to illuminating parking lots.

High Intensity Discharge or H.I.D. lamps produce light by passing electrical current through vaporized gas under high pressure. The different gases or materials contained in the arc tube dictate the colors of the spectrum that the light will produce.


When deciding upon what light source you want to use, you must consider the plants needs. The blue-violet and red-orange segments of the visible light spectrum are the most important for photosynthesis and chlorophyll production.

Red-orange light will encourage flowering and stem elongation. Light strong in the blue-violet spectrum will keep plants short and bushy with short internodal space. In combination the two will produce more balanced growth.

Metal Halide or Multi Vapour H.I.D. lamps provide the most complete spectrum for plant growth from a single source in absence of actual sunlight. Metal Halide lamps produce a decent amount of light energy in both the blue-violet and red- orange ends of the spectrum but, leaning slightly towards blue-violet as the predominant area of spectral energy. Metal Halides can be used for both vegetative and flowering stages.

A definite improvement upon the standard 'white' metal halide is the new Daylight Full Spectrum bulb by Duraguard. This bulb illuminates a very definite blue spectrum resulting in very healthy vegetative growth, with short internodal spacing. Since this bulb has a balanced spectrum it would be a perfect bulb for a one lamp operation. Available in both 400 and 1000 Watt.

High Pressure Sodium or HPS lamps produce light energy weighted toward the red-orange area of the spectrum. Many growers use these lamps for all stages of growth, unless natural sunlight is available we would only suggest their use during flower initiation and development periods. There is a new strain of HPS bulbs that have an augmented blue segment (30% or more) making them a worthwhile choice for all growing periods.

For those who have metal halide systems and want to add or change to high pressure sodium lamps for flowering, there are Retrofit High Pressure Sodium Lamps available that are compatible with a metal halide ballast. The definite advantage that the retrofit bulbs have over conventional H.P. S. bulbs, is that you can use metal halides for strong vegetative growth as they are predominant in the blue-violet spectrum and high pressure sodium lamps, which are high in the red- range spectrum for flowering. Available in both 360 and 940 Watt.


Initial: Refers to the initial lumens of the lamp when it is first arced. (Up to the first 100 hours, which is the burn-in period).

Mean: Refers to the period after the initial burn-in time of 100 hours. This is the actual amount of lumens that the bulb will produce throughout it's life of approximately 12,000 hours.

Colour Temp: Colour Temperature is not how hot the lamp is. Colour temperature is the relative whiteness of a piece of tungsten steel heated to that temperature. Incandescent has a warm (red) color temperature of around 2700 K as compared to Cool White flourescent at 4200 K, which has a cool (blue) colour temperature.

Colour Rendering Index ( C.R.I.): Colour rendering index is a subjective measurement of how well each lamp source renders colours. Incandescent is assumed to have a C.R.I. of around 100 so it will render all colours correctly. HPS has a C.R.I. of only 22, so only 22% of colours will be rendered correctly.

It is important to remember that C.R.I. readings of two sources can only be compared if their colour temperature is equal. You cannot compare the C.R.I. of (C.R.I.=22) vs. Metal Halide (C.R.I.=70) because the colour temperatures are different (2200K vs. 45OOK).

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