Sodium Citrate Mac & Cheese — Silky Smooth

Yes, I've been watching a bunch of food science videos - mostly from Adam Ragusea - recently.

Food science is fascinating. In fact, it was my second choice for a new high-interest, low-homework science class back when Princeton was making a set of new, at-the-time-semester-long science classes about twenty years ago. First choice was material science because I'd just taken the first year workshop from ASM and was geeked about how cool it was.

By the way, they have student camps, too.

XKCD 3144: Phase Changes

Source: XKCD.com

See, it's funny because ice spikes are frickin' weird.

Sometimes, water freezes and makes ice spikes. It's more likely with distilled water than with tap and more likely if your freezer is just barely below the freezing point of water.

Nature doesn't care about your simple theories of how materials work. 

All of our laws about the world are descriptive not prescriptive.

There are more things on heaven and Earth, as it were.

How and why sauces 'break' (or don't)

Last week I posted a video from Adam Ragusea showing that garlic and egg yolks both contain compounds that can emulsify sauces. Linked from that video via YouTube was this video who contains a little more background on emulsions in the kitchen.

XKCD 3242: The Aperiodic Table of the Elements

 

Source: XKCD.com

I want this on my walls.

Hey, students, if you happen to have access to a large-format printer and can turn this image (the highest-res version I can find) into a vector file so it won't lose resolution when it's blown up, I want this on my walls.

See, it's funny (and awesome) because it shows the periodic table in an aperiodic arrangement.

That's funny to us chemistry folks.

How garlic can emulsify sauces (aioli, alioli, allioli, aïoli, toum, etc)

That's a whole lot of garlic there, Adam.

My wife is firmly opposed to mayonnaise in just about any form or dish, so that stuff only crosses our threshold when I buy it - usually in a premade potato salad from Jungle Jim's.

But I'm fascinated by the emulsifying abilities of both egg yolk and garlic, and Adam does a great job of explaining the inherent science in both in this video.

Karen Lise Krabbe: Gelled Glass

That's absolutely fascinating.

I've seen the reverse spherification technique of using sodium alginate and calcium chloride solutions to produce edible, gelled products (Kool Aid worms, gelled drink spheres, cocktail pods). Sometimes the calcium chloride is swapped out for calcium lactate because it's really the calcium ions that are necessary for the process.

But using that process to make gelled glass which can be shaped in ways that glass normally couldn't be shaped is pretty amazing. All respect to Karen Lise Krabbe for developing this technique. If you want to learn more, you can check out her ebook on the technique.

Magical liquid!

Most years, I give my students some freedom after the AP chemistry exam. There's still so much more chemistry to learn, but I've completed the required curriculum for the year, so we can explore a few cul de sacs of chemistry.

We've played Minecraft because they told me there was a bunch of actual chemistry involved - which turned out to be kind of true. There's certainly a whole bunch of material science involved.

I've also had them research chemistry programs as universities around the midwest, practice and perform a demonstration for my non-AP course, and honestly - write a blog post for my chemistry blog. 

Today's post, however, is about the time my students asked if they could just make slime. We make polyvinyl alcohol slime in first year chemistry, but they wanted to make glue (which I recognize is often PVA-based) slime. One of the students said she had a gallon of Elmer's school glue at home from her Covid lockdown slime days (apparently slime-making was a thing for many school-age students during Covid lockdown?)

In discussing what they could bring in, other students in the class offered to provide shaving cream (apparently to make 'cloud' slime - a fluffy variation), small fruit-shaped slime charms, glitter, and non-staining food coloring. I, generous sort that I am, offered my leftover borax solution from the crystal making experiment early in our matsci curriculum. It's a little more than the 4% concentration called for in most slime recipes, but it's close enough.

One of the students asked me if the borax solution took the place of the activator. I'd never heard of an 'activator' solution before, so I started looking around online.

Apparently the borax solution + PVA/glue solution with which I am most familiar has some alternatives - sort of. There's the 'borax-free' variety using baking soda and contact solution, but the contact solution has to contain boric acid - which would be neutralized into...um...sodium borate (aka borax) with the addition of sodium bicarbonate (baking soda). There's also the option to just purchase pre-mixed activators, one of which - shown in the image - is Elmer's Magical Liquid.

With a quick check of the Magical Liquid's SDS, I see that it's a solution of boric acid, sodium bicarbonate, sodium chloride (?), and a couple of anti-microbial agents. The various concentrations seem lower than I would have thought: <1% boric acid, 1-5% sodium bicarbonate, <1% sodium chloride, and <0.5% of each of the preservatives. I'm feeling too lazy to do the math to do actual calculations, but I'm pretty sure the combined percentages - discounting the bicarbonate and the chloride masses - would come out decently below the 4% of the borax solution I'm used. Wonder if that's just a case of commerce allowing for the lower concentration leading to more needing to be purchased.

At $17 per quart (from Amazon as of 6/7/26 when I'm typing this up), the magical liquid has to be a high margin item for Elmer's. It's more expensive if you want your slime to be green-apple-scented. Sadly the cherry limeade scent looks to be sold out and might be out of production now - even though Elmer's still has it listed on their website.

Cherry limeade's my favorite...grape's favorite, too.