film yeast question

hey everyone, first time poster, avid reader, so thankyou for all your ideas and suggestions!

I've gotten to the 7 day mark of primary fermentation. I'm starting small scale (5L demijohns) so I can get some decent recipes before trying them out in a bigger batch.

My issue is an apparent film yeast one. In one of my four demijohns, there seems to be a large amount of build up around the neck. Should I be worried about this? It's a 60/40 mix Apple Juice/Pear Juice, 400g of dextrose was added, with a SG of 0.069 before adding yeast

Any help would really be appreciated

Firstly, you did not measure your SG correctly. A SG of .069 would mean that it was only 6.9% as dense as water. Pure distilled water has a SG of exactly 1.00, and because sugars (and almost anything you'd add to a brew) are denser than water, most brews begin their fermentation at anywhere between 1.045 and 1.065 and ending somewhere around 1.010-1.020.

A film on the edge of the glass or bucket as the Krausen recedes isn't a problem, though most narrow necked vessels are meant to be filled so that when the foam rises, most of the Krausen exits through a spill-hose into a catch basin (creating an airlock in the process)

Most people agree that if you "blow off" the Krausen (the process I detailed above) you end up with a better tasting brew, but it will still come out tasting just fine, that said based on the pictures fermentation is still going strong, you've probably heard/seen this before, but since your doing a 1 stage fermentation time is your friend, I'd personally leave them for another 2 weeks at least before I transferred them to their final bottles/containers for 1-2 weeks (minimum) of carbonation/conditioning.

By the way, what are you using to form the airlock so that bacteria/oxygen cannot get in?

Just remember the golden rule of home-brew, RDWHAHB!

*EDIT* Caught a typo or two I missed when I read it over in the comment box, its 2:00am lol :3

I meant 1.069

Just using water, I've heard of people using vodka or apple cider, but water seems to be the norm.

Thanks for the help Andrew, I think I'll just do what you've suggested and let it sit. First hydrometer reading tomorrow night, so excited to see whats been happening!

Andrew5329 said:

most brews begin their fermentation at anywhere between 1.045 and 1.065 and ending somewhere around 1.010-1.020.

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if by brews you mean beer then fair enough, but ciders that start in that range tend to ferment out completely, to around 0.996 - 1.000