A key part of the cheese making process is pressing the cheese – particularly if you’re making a harder cheese. The purpose of pressing is to force any remaining whey out of the curd, as well as give the cheese its required texture. At first glance it seems like a simple enough problem – you’ve got your cheese in its mould, which may have a bottom and a removable top, so exerting pressure on it is simply a case of putting enough weight on it. But pressing cheese at home is actually quite a difficult task.
On an industrial scale, purpose-built hydraulic cheese presses exert huge amounts of targeted pressure with ease, however during my own home-cheese making experiments I realised pretty quickly that this wouldn’t be a possibility for me.
Early Cheese Pressing Experiments
My first attempts at making a cheese press were fairly basic. Two planks of wood, held together with copious amounts of glue and a few bits of dowel, using some free weights (and apparently a couple of mugs filled with pennies!).
As you can see from the picture, there were clear physical limitations on how many weights you could actually pile on top of the cheese, and when the stack inevitably toppled over, the results were pretty disastrous.
I was never going to be able to exert the kind of pressures required for a cheddar.
Back To School
It was clear that I would have to go back to my cheese-making books and see what they advised – but the process ended up taking me back to GCSE Physics!
The cheddar recipe from Cheesemaking Practise (a fantastic, although expensive, book) mentions a final pressure of 200kPa. Put simply, the pressure required to press a cheddar effectively is absolutely immense.
So what’s a “kPa”? Well, it’s kilo Pascal. And what’s a Pascal you might ask?
Pascal is a unit of pressure (named after Blaise Pascal, above), which can be broken down into Newton’s per square metre. Newton’s are a measure of force which, using Newton’s second law of motion (see, physics in school did have a use!) can be broken down into mass multiplied by acceleration. On Earth, where gravity exerts an acceleration on objects close to the surface of 9.81 metres per second squared, this ends up meaning that a mass of 1 kilogram exerts a force of 9.81 N downwards.
That’s the Newton covered, but we still need to think about the denominator, that is the surface area on which the Newton is being applied. An average cheddar cheese is around 30cm in diameter, so it’s surface area (school maths and physics in one post, how exciting!) can be calculated using pi (remember “pi r squared”?) to be 0.07metres squared.
Now we’ve got all the components of Pascal broken down, let’s get back to cheese making. A cheddar needs a final pressure of 200kPa. That means 200,000Pa of pressure, which equates down to almost 1,500kg of mass on our little 30cm cheddar! Clearly we’re not going to be able to load over a ton of mass on top of a little cheese, so we need some help in the form of mechanical advantage.
Mechanical advantage means a small amount of force can be multiplied through the use of levers, gears or pulleys. Which leads me on to Dutch presses.
The Dutch Press Dilemma
Many of the cheese-making websites and books I read suggest you invest in one of these contraptions (see the one I bought above).
Traditional Dutch cheese presses use a lever to create a mechanical advantage high enough to exert sufficient pressure on the fulcrum (the cheese, in this case) using a small amount of mass at the end of the lever.
Which all sounded great – so off I went and ordered one of these Dutch presses and carefully assembled it at home. But I soon found out that it wasn’t the perfect solution it appeared to be.
Firstly, the mechanical advantage is all well and good, but the practicalities of a free-standing press mean that dangling any serious amount of weight from the lever puts the whole press off-balance, and liable to topple over at any moment (which did happen!). Secondly, the construction of most Dutch cheese presses means the whey dribbles out onto the wood base, which is quite difficult to clean without taking the press apart.
The Customised Solution
So after a lot of consideration and planning, I decided to build a cheese press that would lever directly from the wall of my cheese room, with the ability to lengthen the lever and add multiple weights to the end. That way I could exert all the pressure I wanted, without any concerns about stability.
The general idea was to replicate the lever mechanical advantage of a Dutch cheese press. I sketched out a vague idea on the back of a beer mat with a mate at the pub, then headed to B&Q to scout out what bits I might need. As usual, I wanted all components to be easily accessible, without any need for custom parts.
I wanted something that had minimal impact on my existing setup, so I decided to use different sized square-moulded steel to interlock with each other, cobbled together with a few long screws, washers and nuts to ensure the joint allowed sufficient movement.
Exerting pressure on the cheese would be done by another square steel rod, with some of the pressure being spread out using right-angle brackets. The steel rods needed to be sufficient in size and strength to not buckle or warp under pressure.
After much hacking, sawing, drilling and filing I had what I wanted. Smooth running joints, and a nice long, strong lever to add mechanical advantage.
Attaching the wall piece was pretty straight forward. The walls of my cheese room sadly aren’t brick, but with a couple of good-sized screws it seemed solid enough for some serious pressure. The main lever piece slots into the wall piece smoothly, meaning I can store it separately without interrupting my cheese making.
In testing, laden with 1.25kg of mass, the press exerted 4.528kg of mass on the scales, so a mechanical advantage multiplier of just over 3.6. Not a huge result, but I have plenty of good-sized 1.25kg weights, and the slot-in system has the advantage of being easily extendable with longer bits of steel if required. I could also easily saw off a bit of the short end of the press to increase the advantage easily.
And here’s the finished press in action! So far it seems to operate very well indeed. I’ve just finished making a cheddar with the new set up, and have high hopes. Will post results… in about 6 months! (that’s a cheddar joke, that is!)