Closet Temp..75...rockwool Internal Temp..66...that Seems Low..is It???

I've read countless threads on room temp...consensus seems to be 75 degrees is ideal....so i keep my closet between 73 and 78.....however my rockwool cubes seemed very cool to the touch...I stuck a meat thermometer into the cube and the internal temp was 66 degrees....this seems low but I havent read any info relating to rockwool temps during germination...any input would be appreciated

How wet is the cube? It should just be barely damp. Do you have a heat mat under your cubes? You'll probably need one. Hope this helps

the medium will always be a few degrees cooler than the air. 66f is ok for mature plants.

if for clones you will need to keep the medium temp in the mid to upper70s, same as seedlings

*** start germination by soaking seeds in a glass of water for 24 hours. afterward, wrap seeds in damp paper towel. insert paper towel into plastic zip lock baggie. close baggie half way and place in a warm dark place. wait for seed to crack exposing taproot. insert root down 1/4 inch down in medium. keep medium warm (75-80). dont use lights untill seedling breaks ground.

That sounds about right, your water temp is ideal at 65 degrees, even a little lower won't hurt. Water at 65 degrees hold twice as much oxygen as water at 70 degrees. The rockwool itself doesn't transfer heat or cold, thats why its a good insulation when is is dry. What your are measuring is the water temp in the rockwool, and once you are past 'breaking ground' the temp is fine. VV