Pressing a cheddar is difficult. It's one of the most difficult cheese to press. Commercial producers will literally use tonnes of weight on it. A couple of things to keep in mind:
- The ease with which the curds will knit is a function of pH, moisture level and temperature -- in that order. Cheddar is difficult because you are pressing at a pH of 5.3 and a set moisture level. Your only variable is temperature. So make sure that the temperature is realtively high.
- The amount of weight you need depends on the surface area of your cheese. If your cheese is 10 cm (4 inches) in diameter, the surface area is 79 cm2 (12.5 in2). If your cheese is 16 cm (6 inches) in diameter, the surface area is 201 cm2 (28 in2). To get the same pressure (kg/cm2 or psi) you need more than twice the weight for only a 60% increase in diameter.
A standard pressure for cheddar is 8 psi. If you have a 6 inch diameter cheese, that means 8 x 28 = 224 lbs. So, yes, 50 lbs is generally not enough.
So how does Gavin get away with 50 lbs? He doesn't cheddar long enough, basically. You can see that in his videos. Does that *really* matter? Probably not. If you finish up at a pH of 5.4 instead of 5.3, it's going to make it easier to knit the curds and your cheddar won't be quite as sharp as it could be. Do you care? Maybe, maybe not. Lot's of Gavin's cheeses are not particularly authentic. He seems to be happy making yummy cheese and not worrying too much about the details. I think that's the charm of his videos.
My advice would be to make smaller cheeses, though. Make something in the 500 gram / 1 lb size. Especially if you are vacuum packing it's not going to make much difference in terms of aging and you're going to be able to press it better. Again, keep the temperature up in pressing. I'm not entirely sure what temp is best. At 27 C, the fat in the milk starts to break down. Of course, you've been cheddaring above that temp for several hours, so maybe that doesn't matter. Not sure. I haven't done a side by side. But my thinking is that keeping it at 36 C (97 F) for the first hour or two of pressing won't hurt and will definitely help you close the rind.
You can also play with the moisture level and pH. Slightly larger curds, less cooking, cut the cheddering back just a bit. All of those will help close the rind at the expense of the texture of the cheese and potentially reducing the total amount that you can age it. If you were thinking of only aging it 6 months, for example, I wouldn't hesitate to up the moisture content a bit, or reduce the acidity just a tad.
I think, above all, don't be afraid to experiment. Make a lot of cheese. Usually it takes me at least 5 tries of a style of cheese before I'm happy with the result (I'm *much* more picky than Gavin ;-) ). If you go into it with the idea that you're going to be making 5-10 cheddars, you can sacrifice the first 3-4 experimenting with different techniques. Remember that yummy, yummy cheese curds are simply made from cheddar that isn't pressed. You can eat those cheddars the next day and they will be *awesome*. You can age them out 1 week, 3 weeks, 5 weeks and eat them. They will be *awesome*. Where you run into trouble is when you make a single cheese and try to age it out 18 months. The feedback loop on your learning is too long. You'll be old and grey before you make a good cheese ;-)