mugsys_m8, I've modified your brew day instructions, hopefully this will make sense. What John Drummer says above is spot on, but based on your questions, is perhaps a bit over you head in these early days of brewing (sorry, not meaning to sound condescending, I can only just follow it myself - but while his calcs appear correct, worrying too much about efficiency and the like is (IMHO) perhaps a bit too technical for your second brew!) and sorry JD, no offence intended
I don’t have a Massive kit, I just do regular 5-gallon BIABs with an assortment of kit cobbled together, but the principles are the same.
1) 6.25 litres mash water heated to 72 degrees Celsius
2) Add 2.5kg maris otter in grain bags.
3) Leave for 1 hour maintaining 65 degrees Celsius. Easiest way is to make sure the hat is off (!) and wrap the pot in a big old beach towel or two for insulation. Don't be tempted to keep opening it to check the temp, as you'll just let the heat out.
4) Prepare 6.9 litres of sparge water at 80 degrees Celsius in FV
5) Take grain bags out of mash water and squeeze into mash water to get a fair amount of the water out. Put grain bags in plastic bucket. Put the mash water on the hob and start heating it.
6) Meanwhile… I assume the plastic bucket is your fermentation vessel (FV) doubling up as a sparge vessel? If possible, you might want to have the bag open with the top hooked over the rim of the FV all round, so the bottom of the bag is suspended off the bottom of the FV and you can pour water into the bag. This way the water can flow through the grains and fall into the FV. If the bag is just sitting in the bottom of the FV it will be fine though.
7) Slowly pour the sparge water over the grains in the FV. What you are doing here is getting all the sugars out of the grain that you can. Don’t let this sit for ages, once you have poured the sparge water through the grains, lift the bag and let as much drain out as possible.
8 ) Squeeze the bag into the FV. Put the grain bag in the sink, to be chucked away later on when you get a minute.
9) Add the liquid from the FV to the mash water in the pot, and bring the lot to the boil.
10) If you have a way of measuring the gravity, take a sample and do it now. If not, don’t worry.
11) Add 16g hops and start a stopwatch. This is the start of the boil, zero minutes.
12) At 45 mins add the immersion chiller.
13) At 55 mins Add 34g hops.
14) At 60 mins switch off the heat. Start the chiller. Chill to 20 degrees Celsius.
15) While it's chilling, clean and sanitise your FV.
16) “Pour over hop bags into sterilised FV.” Not sure what you mean here – I think if the kit has a hop bag then you would put the hops in the hop bag and let the bag sit in the pot during the boil. Add more hops to the bag as required during the boil. This allows the water to flow around the hops, to get the flavour out, but means you can easily whip the bag out at the end of the boil and you have ‘clean’ wort, i.e. it’s not full of sludgey hops. Alternatively, if it’s a big straining bag then add the hops directly to the boil. Your wort will be full of sludgey hops, and you will pour it through the bag into the FV, basically using the bag as a sieve to strain the hops out of the liquid. I suspect it’s the first option, especially if the hop bag is smallish.
16) Add packet safale SF-05. Add the whole pack, the yeast is just going to multiply in the FV anyway, may as well give it a head start.
Also, note that during the mash the grain will soak up lots of water, so your 6.25L will end up as about 3.5L. Then you sparge and get most of your sparge water back (as the grain is already saturated so can’t soak up any more water), so you’ll end up with a little over 10L of wort in the pot for boiling. Allowing for say 1-2L of evaporation during the boil, and some further liquid being soaked up by the hops, you’ll end up with about 8L in the FV.