Yes, look up pressing in the pot. Also, it looks like you didn't press until the next day, by that time the curds will have cooled down quite a bit, and they are very hard to get to knit when cool. Basically, to get a good knit on a cheddar type, you need to keep your curds warm (which is what pressing in the pot is about). I get a good knit with only 2.5 PSI, and that's about 77 lbs (35kg) on a 6.25" diameter mould (about 16 cm). So not huge amounts of weight, but a lot more than 25 lbs will be required (for dead weight). When you say 25# pressure, do you mean 25 PSI? That shoudl have knit your curds, even if cold, or do you mean 25 lbs on the follower, in which case you got a pretty good knit for cold curds.