I'm not 100% on what you mean here but you should never let water get on any part of a clone that you don't want roots to grow from. If a few drops fall on them, they'll still be ok, but you want to avoid it.
what kind of sprayer are you using? you are going to want to water them as much as possible while still allowing them to get air and enough so they dont dry out. i'd e nervous about giving it a full 15 minutes of just air. maybe more like a 5 on 5 off cycle. but if your using misting or fine jets as long as you have sufficent bubble stones to airate the water you can have it going 24/7
i have a 37 site cloner that i have 14 360 sprayer with a 500 GPH pump with the sprayers a few inches away from the lid as for timers i i have a digital 7 day one from hydro farm but i dont think it can do a reoccurring 5 on 5 off but im using a timer that is only able to use the 15 on and 15 off or alway on i read a report on this site saying that if on all the time rot may creep up on the stem
what timers are able to do the 1 min on and 5 mins off?
The one I have
the more of the stem exposed the more space the roots have to grow ive seen people do over three inches, but that was also in more of an aero spring setup. you can also split the bottoms of the stem in half about half way up whats sticking down to increase the surface area that can grow roots
going up how high? temperatures betwen 80 and 82 are suppose to help root cloes faster. but temperaturs above 85 can acutally cook the roots. they make water coolers you can buy to chill the water.
atm the temp is at 71 i started out with 69 and that was about 5 EST so its not going up that fast i guess
theres nothing wrong with that temperature but your going to get faster growth with warmer temps. the air temp you still want to be around 72 - 76 slightly cooler than the water. try using like a starter tray heating pad. you can put it on a timer to control how hot it makes the water.
well if your using distilled or RO water and your cloner is doesn't have any light leaks. it shouldn't be problem. just make sure your using aseptic techniques when taking a clone. bacteria and aglae and mold and all that good stuff can grow just as easy at 69 degrees as 79 degrees. bacteria can actually survive freezing tempertures. just like in your refridgerator. food still spoils it just takes longer.