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Comment by kqr | Hacker News Reader

I grew up long after slide rules went out of fashion, but I really like them. And not only for their signaling value; I genuinely think they make working with specifically ratios easier.

For example if you have a recipe calling for 150 g of butter, but you want to use all of your 250 g, you can just align 150 and 250 on the slide rule, and then read off the correct amounts of the other ingredients, without ever touching the slide rule again. No multiplication performed.

I understand people don't use slide rules for more things, but I'm baffled they aren't considered standard kitchen equipment, in one shape or another.

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That wouldn't work in the US, because we measure a lot of things by volume, don't use the same units for everything (small volumes are measured in teaspoons or tablespoons, larger volumes in cups), and tend to use lots of fractions in cooking. So a recipe wouldn't call for 150 g of butter, it would call for 2/3 of a cup. I suppose you could have multiple scales on a kitchen slide rule though.

For American-style recipes you could use something like this: https://www.reddit.com/r/woodworking/comments/5y1r4h/kitchen...

Wouldn't that all still be the same ratio though? If you set the slide rule to convert 250 to 150, shouldn't it e.g. also convert 2 cups to 1.2 cups?

Measuring cups aren't graduated in 10ths. They're split into 8 liquid ounces. 0.2 cups = 1.6 oz.

(My wife, who is from Finland, thinks the measuring system is insane. At least now I'm good at estimating conversion from F to C.)

Your wife is correct. Imperial measurements are absolutely ludicrous.

The US uses customary measures. The UK used Imperial.

TIL

+- 20 % error, insignificant for the accuracies used with either system.

Volume is just base 2 instead of base 10. It’s probably the most sane of the imperial measurements.

I assume you mean the cups that come in various containers of a particular size, because the ones I know come with a scale.

My liquid measuring cups are glass and have a customary scale graduated in liquid ounces, not 10ths of a cup. They also have metric measures on the other side.

Yep. And it would convert 2 tablespoons to 1.2 tablespoons too. There is no reason it wouldnt work for American recipes.

Most American measuring cups don't use decimals, unfortunately. You get things like ¼, ½, and ⅓ cup measures. Of course, still doable, just takes some extra mental work.

And if you can do that much mental work, you probably don't need the slide rule. I think a slide rule graduated with "cooking fractions" (i. e. the sizes of measuring cups and spoons that people actually have) would be a good idea.

https://www.reddit.com/r/woodworking/comments/5y1r4h/kitchen...

Well I use a cooks measure for that allows you to quickly measure different things by volume flour rice etc.

Keep in mind that slide-rules typically have more than one scale. So there could be a scale for volume, a scale for weight- even a scale to estimate cooking times.

Now I want one of these. (Especially the "estimating cooking times" parts - I'm weirdly good at mental arithmetic so I don't actually need this for volumes and weights.)

>>For example if you have a recipe calling for 150 g of butter, but you want to use all of your 250 g,

What a strange way of cooking. I'm not saying it's bad, just that typically people cook for a result (I want to make X servings) not a reason (I want to eliminate all of the butter in my house).

Think of it this way; the last time you cooked this dish there was way too much and youd prefer not to do that again. This would help.with that problem.

I guess it also makes more sense for baking than cooking.

But that's not what this scenario presents. OP was specifically talking about not wanting to leave ingredients around. He's solving a different problem.

All ingredients move together in ratios (got that, totally understand) so I understand HOW this work. What I was commenting on was WHY someone would cook this way. Again, I'm not saying it's wrong, it's just a problem I've never encountered. If I only used 150G of butter and had 100G left, then I have 100G of butter for whatever else I'm cooking.

I'm sure scenarios can be presented for why this is a problem that needs solving (storage space, product expiring, etc) it's never been a way I personally did things.

If you have some ingredients you want to get rid of, make a bigger recipe and have leftovers. If you don't, don't.

I've done this a lot of times.

Basically, the reason is, I want to make as much as possible of something from the ingredients I have. Just find the constraining ingredient, calculate the ratio, and you're set.

But there's so often other restraining conditions. This works better for some things (cookies) than others (a loaf of bread) because of portioning or cooking dishes or other factors.

Again, clearly this is some kind of a thing some people do, I just don't tend to cook this way apparently.

Would you understand it better the other way around? A recipe calling for 250 g of butter, but alas, you only have 150 g left.

Not really? If I have a dinner party involving 6 guests, and my recipe calls for (<ingredients per portion>*6) then scaling down that ratio may give me 4.5 portions.

I don't cook things without purpose/specific goals. I'm cooking to make enough for the people I'm expecting.

That's not to say it doesn't make sense, just not how I've tended to see things cooked.

OK. What if you have a dinner party for 6 guests, but your recipe is written to give 8 portions?

What I'd do in this case (and this is true for most everyone I know) depends on what "portion" means:

- If it's something that can be reasonably divided among guests (such as a soup or something similar), then I eyeball the portions so they're all approximately even. Optionally, if there's an ample amount, you can simply let people decide how much they want through self-service.

- If it's something that's demarcated by physical objects (e.g. dinner rolls, cupcakes, etc), then you have a few other options: Leftovers to save for later, split them among people who want extra, or give them away to whomever wants them.

I don't know about the OP you're replying to, but I rarely divide a recipe up based on expected portions since portion size is highly variable. Should I have extra left over, then I deal with that accordingly. If I'm cooking to get rid of an ingredient, I don't particularly care if I miss the mark by a few portions provided I have enough in the first place for the objective.

(The other problem is that portioning in this question seems to me to assume that all guests are equally hungry.)

That's solving a different problem. Again: I understand how to scale a recipe (which is what you're describing).

Let's do this as a math problem.

How I tend to cook: Xbutter + Ysugar + ZFlour = 20 Cookies.

How OP is cooking: 2 butter + Ysugar +ZFlour = X

We're setting different known quantities (him butter, me portions) and then solving for the rest. They're fundamentally different approaches in cooking philosophy. And again, neither is "wrong" I just found OP's style to be novel enough to comment on

Around our house, we definitely cook with the expectation of having leftovers. While we do plan ahead some, a lot of our meals involve looking in the fridge and trying to figure out something to make with whatever raw ingredients happen to be in there, and hopefully scaling whatever spices/sauces/etc to match. It's only two of us, and we'll often cook 8-10 servings of something to have lunches for the next couple of days.

I do this: recipe calls for 220g of butter, packet I have is 250g; just make bigger batch of cookies.

I just round & then convert in my head though. (Eg 30/220 ~ 15% = a tenth + half a tenth).

I definitely cook this way sometimes, although not with butter. But say I have a recipe that calls for 1 kg of chicken and I have 1.25 kg. I'm going to use all that chicken and scale everything else up by a factor of 1.25, rather than being stuck with that extra 250 g of chicken.

Of course, this only works if you don't mind having too much food. I like leftovers (I get to eat without having to cook!) so it works for me.

This is how baker's percentages work-- you typically start with some quantity of flour like 50 lbs and all the other stuff is available in whatever quantity you need. The problem is getting the ratios right.

No I understand recipe conversion (worked in restaurants for 10+ years) so I understand everything working on ratios. I just rarely in my professional or personal life cooked by saying I have X amount of an ingredient and want to use all of it. I've always started saying "I need X portions of a completed product, and therefor need to have <insert amount of ingredient>).

Replying to you and the GP:

Throwing a spanner into the works, just for fun:

In India (and probably some other countries), cooks often don't measure out ingredients for dishes [1]. They just wing it / use their experience [2] (called andaaz in Hindi/Urdu). And the results are often or mostly good (except with bad cooks, of course).

[1] I guess that approach works for all countries, except individual cases where people blindly follow formulas to the letter.

[2] Of course, they are not flying blind, they use rough (or precise enough) estimates, that are based, again, on their experience, and on just seeing what amounts of what stuff (whether it is pinches, grams, ounces, kilos, pounds, or whatever), makes for a good dish.

Oh sure, but that's a WHOLE other thing. Last night I made potato soup for dinner. I peeled about 2.5 pounds of potatoes, and that was the only thing I specifically had in mind for "will this be enough portions of soup for the people I'm trying to feed" when I started, no measurements or ratios. Everything else was just me leaning on all my experience to make it taste the way I wanted.

That's a whole different style of cooking, and most people don't get there until well AFTER they learned how to cook something with a recipe (or someone telling them how many handfuls of beans to add to the pot).

Good points, and I agree. I meant roughly the same, when I said "use their experience" / "andaaz", although did not make it explicit.

I'm not great with mine, but I really love using them. I took some of my engineering finals with it and finished well and quickly.

They just make the calculation more "real" and I feel like I'm actually working out the problem instead of just punching numbers into a thing that gives numbers back.

Not all ingredients scale linearly. You would also need a scale exponent.

Slide rules usually have quadratic and cubic scales.

They do by weight.

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