Metal Halide lamps for printing

Base: "Perforated Plate" (Lochblech) made out of steel or aluminium
https://www.amazon.de/Lochblech-Aluminium-Zuschnitt-individuell-günstig/dp/B077LZS83J/ref=sr_1_6?__mk_de_DE=ÅMÅŽÕÑ&keywords=lochblech&qid=1562216680&s=gateway&sr=8-6

As lamp holder I used 5 x sera reptil ceramic holder https://www.sera.de/de/produkt/terrarium/sera-reptil-ceramic-holder/ but it was not easy to cut the big holes, because the base was steel.
Better way would be to use sockets like these: Trixie 76105 Porzellanfassung Pro Socket https://www.amazon.de/Trixie-76105-Porzellanfassung-Pro-Socket/dp/B003OAGDHC they can be installed at the back, so the holes can be smaller.

Picture of that device:

Two steel rods and four lab stands are used for holding
Edit: The shadows at the picture where artifacts, from the 50 Hz frequency in the digital camera....they where moving at different pictures.

Here you can find the UV-power of the lamp:
https://www.osram.com/appsj/pdc/pdf.do?cid=GPS01_1028569&vid=PP_EUROPE_Europe_eCat&lid=EN&mpid=

And yes the blues are very dark...but I use a different cyanotype recipe: See Variant 1 at http://illumina-chemie.de/chemigrams-and-co-t4590-s15.html#72786
After testing the 6% concentration I reduced it to 4% http://illumina-chemie.de/chemigrams-and-co-t4590-s15.html#72823 (only in German) Reason for that: The 6% where to much, so the emulsion was to sticky (doughy) for spreading it with a brush.
One disadvantage the picture is sometimes touch sensitive when wet, if you touch it you will wipe away the blue layer.
Advantage: The gelatin fixes much pigment at the paper....
bj68

The hydroponic stores deal with the public, which is why they won't sell any lamp that puts out a lot of UV or isn't suitable for an open fixture. Also, when they say a lamp has 15% more blue or UV or whatever else can make a stoner think that they will get better results, remember that 115% of next to nothing is still next to nothing.

If you want as white a light as possible from the hydro store, check out the 315w 'light emitting ceramic' lec lamps. Reassuringly expensive. Very long lamp life. Takes about 8,000 hours to drop to 80% output and that 80% will stay around 80% for many years to come.

It takes some minutes for hid lamps to reach full brightness. It's also recommended to give 30 minutes between switching them on/off or off/on.