Higher than expected ABV

[AdamR]

Since I moved on to all grain brewing, everything I brew ends up being pretty strong.
I mainly use the DK Home Brew Beer book, that I think alot of people have for recipes.
As an exampe, the last brew I bottled was the '60 minute IPA'.
My OG was 1.068 and FG of 1.006.
An online calculator gave me an ABV of 8.14%
The book gives me an estimated ABV of 5.7%
I'm not really complaining; my beers taste good, but more sessionable beers might be a more sensible option?
So, if I were to reduce the grain bill by a percentage would that sort it out?
Are there any easy calculations to use?

[Underground Joe]

You're getting very good attenuation from the yeast. What is your mash temperature and what yeast are you using? Also are you using any sugar in your recipes.

[AdamR]

My strike water temp is always 72C aiming for 65C mash temp (sometimes a little high at the start).
Fermented with Gervin Ale Yeast from wilkos in a kitchen cupboard.
No sugar other than priming sugar when bottling.

[Charles1968]

Something doesn't add up here as you need high efficiency to even get the predicted 5.7% from that recipe, never mind 8.14%. Your measurements are out so you need to find out which one. Probably not your scales as you presumably can see the weight of the grain on the packaging. maybe your hydrometer is out and the beer is actually fine. Have you checked reading the gravity of plain tapwater? It should be 1.000. Another possibility is your water volumes are wrong. You should get 23 litres (40 pints) from that recipe - does that match what you've got in bottles?

[basswulf]

What was the target OG? You might want to dilute your wort down a bit before fermenting or, better yet, get a bit more water in at the start of the boil.

Also, what temperature are you fermenting at and for how long? When I used some of the Gervin yeast from Wilkos earlier this year, I got down to 1.008 but only from a start of 1.038.

Wulf

[Charles1968]

The recipe in the book makes 23 litres of beer and has a very simple grain bill - 5.5 kg of pale malt. Target OG isn't given but should be about 1056. It isn't necessary to dilute the brew length to bring the OG down, the figures all add up in beer engine. Fermenting at a higher temp isn't the problem. Most likely the water was short or too much grain used.

[basswulf]

If your initial measurements might have been suspect then all bets are off concerning the recipe. Beer Engine has a good reputation so perhaps next time you should be extra scrupulous about the measuring grain and water. Like a carpenter, take the time to measure twice before you cut once.

Too much grain AND too little water could add up to a noticeably higher gravity wort, especially if you're boiling regime (surface area, heat applied, atmosphere of your brewing room) also gives higher than expected evaporation.

Wulf