First, I wet the mix really well, and fluff it to release all the dry mix underneath, rewetting as necessary to make sure it's all evenly moist.
Then, I nuke it in a old microwave oven for 20 minutes. I use a large hard plastic popcorn bowl that can take the heat. After it's nuked, I fluff the mix quickly to release the steam, then cover the bowl with a clean bucket lid to hold in the steam. Let this rest as you move on to another batch.
After 10 minutes remove the lid, quickly fluff up the mix a bit to release the steam, and re-cover. By the time the second batch is nuked, the first batch has finished the sterilizing process. I fluff it again to cool it a bit more, then fill my seedling trays.
The seedling mix is warm when I sow the seeds, and I water them in with warm water, as well. Then, I quickly shove them into plastic drawstring bags and tie them up, either venting open on one end, or tearing a couple dime-size holes in the plastic. This sets up humidity, and seems to hold the warmth inside the bag (see picture below). I noticed fast germination last season, and wondered if it was the heat inside the bags. When my tomato seeds came up, and I vented the bags, I stuck my hand inside. I could feel the heat built up in there! In any case, all of my 212 tomato and 65 bell pepper seedlings germinated.
I sowed 15 cabbage and 15 cauliflower seeds in the Gardener's Supply APS Deep Rooting System. I like this system because the seedlings develop a really big root ball, compared to seeds rooted in shallower cups. I only have two, and am considering getting another one or two.
I also sowed Broccoli seeds in two different containers. Nine seeds were sowed in a deep 9-cell tray, almost as deep as the APS system. I really would like to find more like this one. Nine more broccolis were sown in 8 oz. Yogurt cups.
Then I remembered friends who were expecting seedlings, so I sowed 12 Catskills Brussels Sprouts and 12 Calabrese Broccoli seeds in 6 oz. yogurt cups for them. The cups are in cat litter trays that I placed in a clear plastic, drawstring bag. I labeled all the seedlings with plant markers made from cut up vinyl mini blinds I bought at a local resale shop for $5. From the looks of it, I'll have a lifetime supply. Just write the info on the end with a sharp #2 pencil. That graphite does not come off easily! And, it won't fade in the garden, either.
I'm toying with sowing some Collard and Mustard seeds, tomorrow, but not sure I should start them so early. They grow so fast, I'm afraid they'll outgrow my light stand before I can put them out. I don't want to set them out in this heat, and I'm not sure it'll be cool enough in 8 more weeks.
I'm praying for the same success this season, as last!
Godspeed and Good Harvest!