I think I must have forgotten to replace it when I checked and rotated them the other day. This happens every year to me, it seems, second time this year already. Earlier this month it was a thermostat that went wonky and displayed 0.0 degrees. Probe was in place but did not matter, it kept reading 0.0. So of course it turned on the heat mat constantly. That was under the broc/caulif/cabbage. The cauliflower in the middle took the brunt, but seems to have recovered, most of them.

I replaced that one with this "better" one with heat/cool options plus alarms. It seems much better quality, at least this time it was my fault. If they alarms were set properly, it would have shut down.

So it has been about 10 days now and all but 7 seeds have germinated or are starting. At this point that is over 90% germination, which I am happy with. Not sure if I will get any more, but at 10 days it seems unlikely, although I have one that is still uncurling, so you never know. I guess I don't see any reason at this point to change how I start my seeds, despite the helmet heads. I will keep the plastic on longer in the future as I did this year to keep the seed coats softer. The helmet heads were much easier to remove this year, and actually might have shed themselves eventually if kept moist, but I do notice that if I do not remove them the cotyledons can become deformed.

some varieties take 14 days to pop up.
I have done oops in the past and discarded soil with seeds then ended up eventually popping.
Naturally not labeled at that point.I was in a hurry to get the seedlings out and into bigger containers.

I started some old seeds yesterday and have them in a tray on heat.
soil temp 77 degrees F

I started 3 more seeds, just one cup, of KB today, as well as 6 seeds of a new Ukrainian Heirloom variety I received solovey razboynik. Just one KB seed came up for some reason and I don't like relying on a single plant. The first ones to geminate already have teeny tiny little true leaves sprouting. It is 7-8 weeks from plant out for me right now, so it is basically now or never for the seeds. I put mine at 80 degrees on the heat mat but since I lift the plastic at least a couple of times a day, it drops the temp and it takes a while to get back up. But I don't want to wait 4 or 5 more days to find out I need to start those KB seeds again. If anything I would prefer to have more than i need than not enough.

I am starting some more seeds today. The overheating ruined a good portion - the ones that were up seem fine, but a lot of seeds cooked. I decided to do some testing.
2016 and 2017 sweet pepper seeds and some different sweet pepper seeds from last year. Trying a method I read on tville for pepper and eggplant seeds;
boil water (it was actually weak chamomille tea I had left over from watering)
let it cool to 130f, add seeds (i folded multiple varieties/types in paper towels, then folded, used a rubber band, and marked type)
let it cool to 104f, put lid on a can
let it set 8 more hours before planting (mine set probably 12 hours)
The seeds were very soft but not cooked.
In soil blocks with 1/2" divots, I put three per block. 50 blocks per tray.
Three rows (15 blocks) I covered with "food grade DE".
Three rows covered with perlite.
Three rows covered with my normal soil block mix. (control group)
One row uncovered, just squeezed shut.

I have eggplant soaked too, going in next. I don't know if tomatoes need this, they are pretty easy to sprout, usually 3 days the way I normally do it.

Wow, complicated seed starting methods. I put my pepper seeds (only 2 cups of Anaheims) on the mat with my tomato seeds, exact same planting methods and care and they have all germinated too. Interesting how one method can work so well for one person and not for someone else.

single precious plant, you have the option of cloning once the plant gets bigger- to reduce anxiety.
I don't plant until memorial day weekend.

Yes, late May is when I usually get them out, but i try not to wait until Memorial Day if I don't have to any more. That is traditional around here and the general rule of thumb I grew up with. But then I don't get my first fruit until well into August. So if weather permits I will often get them in a week earlier. I keep hoping for mid May but I can't remember if I have ever actually been able to do that. I look at the long range forecast but it never seems to work earlier. At least not so far. I just checked and according to my garden journal May 20 was the earlies and that was about 10 years ago. Last 2 years May 26-27. For me, what prevents me from getting them in earlier many years is the early to mid May weather. It isn't warm enough to get them hardened off to the sun sufficiently to safely get them in the ground. Once I rushed it a bit too much and had a lot of sunburned leaves. They recovered but I think I just lost time while they did and I didn't end up harvesting any earlier. I was afraid I was going to loose them all and it just wasn't worth the anxiety, lol. So now I harden off as soon as I think it is safe and make sure I get them into the sun gradually and into the garden as soon as I can. But my goal is to have them ready for hardening off before early to mid May, May 15th at the latest, and plant out between May 15 (In my dreams, lol) and May 30.

walk on the ground barefoot.
if it is comfy,it will be for plants.
rule of foot.

Never thought of that Slugworth!

Many times I tried to cheat and plant early,to take advantage of the sunlight vs grow lights, but the plants get stunted if they manage to survive.
Last year in early May, plants in containers actually got diseased and never made it to planting time in ground.

JR, when do you expect the pepper seeds to sprout and then "pot up" to real soil?

The first trays of peppers were started rather early for me, mid- March, and I probably didn't "need" to start more, I probably have enough that made it, but I just bought a bag of DE and remember past discussions regarding its use for seed starting.

I'm figuring 3 days for the sprouting, which is the time frame newwestgardener (original thread last month http://www.tomatoville.com/showthread.php?t=51347) said is all it takes with the hot soaked seeds. I put them all on heat mat at....76f I think. They are all in soil blocks; the variable is the divot where the seed goes is covered 4 different ways - DE, perlite, added mix, or just pinched shut.

My normal way is dry pepper seeds, either from a pack or from a dried pepper core with seeds attached , under 1/4 of wet mix in a soil block, and that takes 6-10 days for most pepper seeds at 80-85f. So I don't really have a proper control group, since all the seeds were soaked and this is lower heat than usual. The problem with my usual method is like this thread's main query - how long do you keep the heat mat going? How long to you keep the dome on? All that time, to me, is the danger zone. Some seeds start right away, while others in the same tray show nothing. If this method works really well to get everything up, fast and on the same schedule, quickly off heat with plastic removed, then it would be worth the effort.

My soil block mix makes a tray worth of 50 two-inch blocks. The scoop is an old cut coffee can (plastic blue maxwell house) that holds approximately 24 fl oz.
2 scoops peat
1 scoop perlite
1 scoop screened vermicompost
1-2 tbsp of lime
dry mixed, then 5/4 scoop of water added, rest 5 minutes to wet out, then make blocks

The seedlings will grow in the flats until plant out in mid-late May. I don't pot up. As soon as they get some real leaves and it is warm enough, I put them outside in a plastic greenhouse outside, hopefully never to return to the basement due to adverse weahter. With the vermicompost, I don't fertilize them at all. They'll be about 6" tall when I plant out through plastic mulch and put an AG19 tunnel over them.

restart/test two trays, one romani, one marconi, 76F with domes. Foreground from left: DE, perlite, added mix, or just pinched shut.
two weeks+ antohi romani survivors. I started them and three other trays on a 4 ft mat. After a week, the mat hit 110F for a day or two because I left the probe out - I cooked 30% of this tray that were slower to sprout. These have been shuffled to save the survivors, it was more random of course. The marconi tray was slower to germinate and is worse off. Mixed hot pepper tray, did okay with the 110F. Jalapeno tray was started about 4 days earlier, so was mostly up, and looks okay.
broc/cauli/cabbage started ~march 1. Using fusion power's method, these started almost immediately, cauliflower just a little behind. These had the thermostat "fail on" while cauliflower was just starting. Most survived, but cauli in middle is rougher. I had to bring them inside from green house tunnel due to this cold. Heat mats are essential for me, but it would be nice to tighten up the sprouting window to reduce the danger zone when a heat mat system failure can cook seeds and a dome might cause damping off.