Using the Raku Process to Show Oxidation-Reduction

A little while ago, I went looking for a video to explain the oxidation/reduction aspects of raku so I could assign it for my students to watch while I was out of the classroom for a day.

Sadly I didn't find one, but I did come across this video from the inaugural ASM teacher camp in Butte, Montana. It doesn't explain the redox aspects of raku - though the title suggests that it might - but it does include your friendly, neighborhood blogger in his orange polo shirt (ASM-branded, natch), and jeans.

Because the video doesn't explain the science, I'll give a quick version...

• We use a clear glaze into which we mix oxidized metals (cobalt oxide, iron oxide, copper carbonate, nickel oxide, etc). Each glaze gets just one of those oxidized metals.
• The pottery is taken out of the kiln while it's hot - somewhere around 1050 ^oC. At that point the glaze is molten, allowing oxygen to leave the glaze.
• The hot pottery is placed into a metal can with something flammable. In this situation we're using torn up newspaper.
• The torn up newspaper catches fire and starts to consume the oxygen in the now-sealed can.
• The carbon and hydrogen from the paper continues to 'search' for more oxygen, so it reduces the metal in the glaze and takes the oxygen from the oxidized metals. (This only works if the pot is hot enough for the glaze to stay molten in the reduction environment.)
• The glaze cools, sealing in the now-reduced metal within it, leaving - hopefully, if everything works right - reduced, shiny metal in the glaze.
• The pottery is quenched in water to lock in the final version of the metal within the glaze - either reduced or oxidized metal.

You can see lots of versions of raku pottery on other blog posts.

What's 'activator' or '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.

Metal in Movies is WRONG

I know that you'll be shocked to hear this, but sometimes things in movies aren't real.

Go ahead, take a moment to let that sink in, to let the shock wear off.

In today's video Nate From the Internet addresses times when metals aren't dealt with appropriately in movies - primarily because of the density of heavy metals like gold and because of the black body radiation that should be given off when metals are hot.

I had noticed a couple of these myself - the 'molten' gold in The Hobbit and the weight of gold in The Italian Job 'remake' - but neither took me took much out of the movie. In the case of The Hobbit, it's because I wasn't enjoying the movie anyway. In the case of The Italian Job, it's because the cast is just so darn charismatic that I enjoyed the movie anyway.

Every Jewellery Metal Ranked (Some Are Terrible)

I don't know Mason Mignanelli from Adam, but he clearly knows more about working with metals for jewelry than I do.

As an aside, sources seem to say that jewelry (as my browser wants me to spell the word) and jewellery (as Mason spells it in his video title) are both correct, but that the shorter spelling is more prevalent in the US (where I am) and the longer is more prevalent in the UK (where I assume Mason is).

As a warning, the video does have a couple of spicy words at 1:30 (s*** - spoken), 1:40 (s*** - spoken), 5:55 (s*** - spoken), 6:30 (s*** - spoken), and 7:20 (kicka** - shown on screen).

tl;dr - no one metal is perfect. They all involve tradeoffs or workability/hardness, cost, and appearance. 

Perfect Aircrete, Kitchen Ingredients.

I've said it before that I'm not much of a DIY-er, so I'm not likely to make my own cement blocks to build anything, but I like the idea of trying this as a project with my students to balance strength/weight/cost in a building material.

The short version of the above video is that a version of aircrete can be made with xanthan gum, rubbing alcohol, water, dish soap, and cement with some vigorous mixing (a kitchen blender, a drill with a drywall mud attachment, or a smallish cement mixer).

The pastry and marble counter myth

I demonstrate something like this in my classroom using Flinn's ice melting blocks and a knock-off MiracleThaw from a second-hand store.

As one of the comments for the above video notes, "Thermodynamics is often very counter-intuitive." 

See, it's funny because Adam's talking about counter materials in the kitchen.

I'll wait while you laugh.

Remember, vinegar leg on the right.

Color Changing Glass - Rocks in a Box 30

I make glass in my classroom.

I've made glass colored with cobalt oxide (dark blue), copper (II) oxide (light blue), chromium (?) oxide (green), manganese (?) oxide (purple), and silver nitrate (disappointingly colorless).

I've not made any glass with neodymium oxide, but I'm thinking I want to do that as my next experiment.

Anybody know of a better, reliable, cheap source of neodymium oxide than these sources? I'll be honest that 1/2 a pound - even 1/4 pound when we're using less than a gram per batch - would last me pretty much forever.