Fully Foiled

I finished the trial seed-starting glow box yesterday- it took another $9.00 of foil backed polystyrene to build out the front and top.

The crudely constructed box in action:

And with a speedling tray full of 128 early spring seeds (short season cabbage, lettuce & chard) and two types of peppers in vermiculite (Ancho/Poblanos and more jalapenos, since we are down to maybe 200 poppers left in the freezer.)

(The two lettuce seedlings are late sprouters leftover from earlier starts.)

I like the high volume/open bottom speedling trays for quantity / early transplants. I use the vermiculite for germination of peppers and tomatoes and carefully move the sprouts to soil blocks for the bulk of their indoor life. More on this later…

I have the lights on a timer to be on for 16 hours out of each 24. The HO fluorescent bulbs are intense (an 1800 watt equivalent between the two) but are significantly cooler than the other main high output grow lights ( HID fixtures like metal halide and high pressure sodium).

The handy soil temperature thermostat control is inline with the heat mat and ideally I can work this to be fairly automatic (ie not cook things).

When it was first set up, the soil temperature was only:

Later that evening it had increased to:

Perfect, right?

Yes, but only if it stays there.

It didn’t. This evening it was 88… not good.

The soil wasn’t warm to the touch though; it appears that my “cooler” lights actually turn this box into an Easy Bake Oven*.

The temperature dropped 3 or 4 degrees immediately upon opening the box, so it would appear I have 88 degree air in the closed box and soil that is much cooler. The mat wasn’t even coming on, so I adjusted things a bit to try to get a better balance.

I pushed the probe a little deeper into the soil so that it had no exposure to the air temperature and then raised the lights a few inches. The last thing I did was to leave a crack in between the top and front panels to vent a bit.

After 45 minutes I checked and the soil temp was 81 and I could feel heat venting from the crack, so I think I’ve got it a little closer to where it needs to be.

*Sidebar:

I was shocked to learn that modern feminism didn’t kill the “Easy Bake Oven”; it is alive and well and even has its own website complete with promotional videos. Wow, who knew? Presenting the Modern Easy Bake Oven