No fermentation

Hello,

I pressed 4 gallons of juice yesterday which was a mixture about half and half of dessert apples and some rather more tart, sour ones but not quite cooking apple tartness. I've not added any yeast and am relying on the natural yeasts but there's nothing happening at all with regards to fermentation. This is my third batch and I've had no problems with the previous batches which bubbled and frothed away very quickly overnight. However, they were pressed about 6 weeks ago when the weather was a bit warmer so I'm wondering if it is the low temperature? Should I wait a couple more days before doing anything? And does anyone have tips about how to raise the temperature of the demijons slightly? Thanks

It's the temperature. Some form of heating pad, fermentation strip, tub of warm water, etc. is about the only way to warm it up.

you should wait. natural yeast ferments can take as long as 7 days to start. They taste better if they go slow, so if you do warm it up to start, cool it back off for the ferment

Well with cultured yeast we tell folks that https://www.homebrewtalk.com/f39/fermentation-can-take-24-72-hrs-show-visible-signs-43635/, and since yeast is yeast whether it is cultured or wild, the same need to reproduce applies.

It's called lag time and it is perfectly normal.

And despite your previous experience, I caution people to realize that since we are dealing with living micro-organisms, EVERY FERMENTATION IS DIFFERENT, and one should not worry if one fermentation acts or starts differently. When dealing with nature there is always a wildcard factor, so you shouldn't immediately assume there is something wrong because one fermentation is acting differently.

Take David's advice and warm the fermeter up, and watch for the bloom.