Great tip! I love the idea of a cookie rack as a "heat spreader! I've been looking for a suitable slab of sheet metal for a few years, but your idea should work better.

Maybe find a store that sells or "recycles" used appliances. They may have a stack of cheap wire shelving from ovens and old fridges that could not be fixed and have been cannibalized.

For any kind of heat, you can get twice as much heat from it if it sits on top of a good insulator. Wood would do, but wood has gotten expensive. "Sheet rock", a.k.a. drywall, a.k.a. gypsum board, is a great insulator, and is also fireproof. Lay down a 3/4" sheet or 1/2" sheet of drywall, then your mat, then the cookie rack, then something waterproof, THEN your trays of seedlings.

Assuming that you're spreading one heat mat over several trays, you might want to capture all the heat you can. Heat rises - that is, heat is lost to the air, and warm air rises, carrying away the heat.

If you can make some kind of tent over the whole stack trays and heat pads, the warm air will be trapped and your overall temperature gain will be much greater.

However, humidity will also be trapped and air circulation prevented. That will cause damping off and even mold. You'll have to strike a balance between heat efficiency and the required amount of air circulation. Maybe some deliberate vent holes or intermittent venting with a fan.

Hey Linda! Good to see you. I thought you'd vaporized.

Karen

Hey Rick, I do hope you're saving your bubble wrap. Works great for draping over flats to help hold in the heat overnight.....which helps cut down on my GH heating costs! (Of course, that only works if you already have humidity domes to keep the bubble wrap off the seedlings!)

And you're leaving out a minor detail: you need to have a greenhouse.

K.

I want a greenhouse!

I do save bubble wrap, and I should use it on the trays I put on my one heat mat. I don't have enough humidity domes, but I have plenty of 18" wide Saran Wrap, and min i-blind slats cut narrow enough to fit even in the little cells in a 128-cell plug tray.

Never do it the easy way if there is a cheaper "MY way"!

I worry that I don't have a soil thermometer ...

BTW, my bubble wrap is mostly anti-static bubble wrap. I have no fear of electrostatic damage to my seedlings!

Aw, Karen, you're just jealous!

Gee, Rick, you don't think a little *zap* might actually stimulate your seedlings to unprecedented growth?

I do like the idea of using the cookie racks, tho! I have some heat mats that I got cheap that really get too warm, and a cookie rack would work very nicely to moderate the heat! Think I'll look around at the goodwill for some spare racks!

And Rick, you can use the outdoor probe from one of those inexpensive indoor-outdoor thermometers to monitor soil temperatures. Our local hardware store has them for around $10. (At least that's what they USED to cost; sigh, haven't looked lately )

>> the outdoor probe from one of those inexpensive indoor-outdoor thermometers

AHHH! Good idea! I was going to steal the meat thermometer when Becky wasn't watching, but the difference between 75 and 90 is barely big enough to see with my eyes ... and probably off by 10-20 degrees!

>> Gee, Rick, you don't think a little *zap* might actually stimulate your seedlings to unprecedented growth?

(Gene Wilder / Young Frankenstein flashback)

"It's A L I I I I I I V E !!!!"

Maybe so, Woofie! But with the storms and wind we get, just keeping a roof and siding on the house is challenging enough. I can't even imagine a small greenhouse weathering our conditions. That's why I've never seriously considered a greenhouse or even a coldframe.

Karen

I've used a heating pad practically forever in this drafty old house. Never thought to use a cooling rack,tho.Good thinking!

Most of the heating pads nowadays shut themselves off after a certain amount of time. Irritating, sometimes.

Most excellent idea .. I use heating pads too! The newer digital heating pads have an auto shut off which can be a problem. I contacted all my kin and was able to get 2 more analog. I only turn mine on at night since I keep the house cold at night .. in the morning the temperature is usually in the upper 70's.

The best thermometers are darkroom thermometers ... they are not easy to find anymore since everything is digital. They are encased in glass and I usually bury one in a pot with dirt (you want it in the middle of the pot not touching the bottom) in the middle of my seed cups. You can probably find one online.

I use those extra large zip bags you can get at the dollar tree.

I understand, Karen. A normal GH wouldn't survive the winds we get here, either! I remember reading a thread a while back where a guy had one of those small Harbor Freight greenhouses and the winds blew it over! Mine is really not a proper greenhouse, but it's a wood-framed building with clear siding.....and it's HEAVY!!!! And it has been a pain trying to add additional layers to insulate it, and the wood attracts wasps. Sigh, it's a pain, but our growing season is so short, it's really the only way I can grow a lot of the things I want. And DH insisted on getting it for me....I think he thought that would get the plants out of the house.... Dreamer!!!

All the heating pads I've bought since the 90s have had shutoffs after an hour or less.

If you or someone you know is electronically inclined you can usually find instructions on how to bypass the auto shut off on the net.

AHA!

I use several of these cheap heat strips. They work great for me.

http://www.wormsway.com/detail...

Karen

Also, someone told me that I could use the "pipe wrap" under a towel.....

heat tape made for winterizing water pipes is what i use . you get it at lowe's or home depot . it is much cheaper than heat pads or heat tape made for greenhouses and works great . i put it on my tables in the greenhouse under a layer of sand .

I have starred everything on this thread! I need to get better at seed-starting. I suck at it. I think the heat mat will help! Thanks. btw, check with metal/junk/appliance haulers. Many ovens are given away with their racks.