How to tell if a cider is finished without hydrometer

Question

EDITED

I have a cider that I have made following the steps on CraigTube for his Hard Apple Cider. The only difference is that I have used Champagne yeast and the batch is 22L. I know you are all going to say to check my hydrometer reading but unfortunately I smashed the hydrometer before I could take the initial reading. The airlock still has activity and is still bubbling after 18 days. It is bubbling strongly every 13 seconds. How will I know when it is done. Should I wait until the airlock has no activity at all?

Recipe here:

21L Juice (7bottles)

Yeast Nutrient (Boil up raisins (that don’t have sulphite on them) and small amount of water, mash up the raisins and simmer)

10- 14Cup’s corn sugar or dextrose (the more sugar the more kick it will have)

1 Lalvin EC1118 Yeast

Steps

1. Boil up yeast nutrient and mash up raisins
2. Take out a little juice from the bottle and add sugar.
3. Shake out the sugar(even do this for the fermenter batch as it saves time and stiring)
4. Put in the yeast nutrient(make sure that it isn’t still too hot) and shake the bottle
5. Add the yeast and shake the bottle a. If you are making a fermenter size batch then pour it all in the fermenter
6. Leave that until the fermenter has stopped bubbling and leave for a few days.

Ok I have done a small scale test. I have had 1.5L of juice and 1cup sugar(200grams) The reading was 1.092. This test does not include the boiled up rasins.

Ok so another reading has been taken. This is 1.000

Answer 1

Even with champagne yeast, fermentation shouldn't take more than a couple of days to complete fully. At the eighteen day mark, what you're seeing is degassing of the cider, where residual CO2 from the fermentation is escaping the liquid, not fermentation. At this point, your cider has complete fermentation, and should be aged as necessary before being bottled/kegged off for consumption.

Of course, the only way to verify this is to purchase another hydrometer, and take readings. If the measurements don't change over the course of 2-4 days, you'll know that the fermentation has completed, but judging by your disclaimer in your question, you already know that.

Update: After seeing that your gravity is at 1.045 after 18+ days, your cider is not degassing, but still fermenting. As far why it is still fermenting after 18 days, I would guess that raisins did not provide enough nutrient to the yeast. Cider by itself lacks a lot of essential nutrients needed by the yeast to ferment fully, and quickly. At this point, I would recommend making the purchase and getting some commercial yeast nutrient. There are many different brands of it, most of which are very effective.

If you cannot get any yeast nutrient, your best bet is to be patient, and wait until you hit a terminal gravity where the gravity stays steady for a couple of days. At that point it has fully fermented. With a high gravity of ~1.092 (according to small scale), you are going to want to let it age for some time before consuming, so it doesn't sound like you should be in any hurry to see it ferment out all the way, so long as it does.