M: Average size russet potato at 375, how long would it need to bake?

G: TL;DR: a typical russet (≈10–12 oz) at 375°F takes 60–70 minutes to bake through.

Details (brief):

Size adjustments:

Texture note:
375°F gives a fluffy interior with a moderately crisp skin. If you want extra crisp skin, finish with 5–10 min at 425°F or start at 425°F for 15 min, then drop to 375°F.

じゃがいも を 焼（や）く。— Bake the potato.

M: I'll just microwave it, then.

G: Yep. That works.

Microwave russet (average size):

If it’s still firm in the middle, add 30–60 sec bursts.

Skin reality check: soft, not crisp.
If you want some skin texture without committing to a full bake: microwave to done, then 5–8 min in a hot pan or toaster oven with a little oil.

電子（でんし）レンジ で じゃがいも を 温（あたた）める。— Heat the potato in the microwave.

M: I said 375 because we're cooking some meatloaf muffins at that temperature. Could I do the skin texture thing there? And if so, how long would it take?

G: Yes. That’s actually a good use of the oven you already have on.

Method (best balance):

  1. Microwave first until the potato is fully soft
    – ~8–10 min total for an average russet, flipping once.
  2. Rub lightly with oil + salt.
  3. Put it in the 375°F oven alongside the meatloaf muffins.

Time at 375°F (for skin texture):

Since the inside is already done, you’re only dehydrating and browning the skin, so there’s no risk of undercooking.

Placement tip:
Put the potato directly on the rack if you want maximum airflow; tray is fine if drips matter.

皮（かわ） を パリッ と させる。— Make the skin crispy.

M: And is 20 minutes good for a meatloaf in a muffin tin, or is that too much, too little, or what? Go online if you need to check that out.

G: Yes — 20 minutes at 375°F for individual meatloaf muffins is in the right ballpark and often perfect if they’re standard-sized and not huge. That’s consistent with multiple trusted muffin-tin meatloaf recipes that finish in ~20–30 minutes at similar temps until they’re cooked through (to ~160–165 °F internally). citeturn0search7turn0search15

Here’s a quick guide:
🍖 Standard meatloaf muffins at 375°F: 20–25 minutes — check with a meat thermometer; they’re done when they reach 160 °F inside. citeturn0search15
🍖 If your muffins are slightly larger or heaped very full: you might need up to 30 minutes. citeturn0search25

If you have a thermometer, that’s ideal — when the internal temperature hits the safe number, they’re done no matter the minute mark.

And yes — while the meatloaf muffins are baking, your pre-cooked potato skin can crisp in the oven (15–20 minutes at 375°F) just fine too. citeturn0search22

M: If I'm doing three potatoes, how long should I microwave?

G: TL;DR: For 3 average russets, microwave 15–18 minutes total, rotating.

How to do it cleanly:

Most microwaves land at ~16–17 minutes for three. If one lags, just pull the done ones and finish the stubborn one solo.

After that, your 375°F oven for 15–25 min will handle skin texture just fine, as discussed.

電子（でんし）レンジ で じゃがいも を 三（みっ）つ 温（あたた）める。— Microwave three potatoes.

M: I've got the rotating tray in the microwave, so all I need to do is flip them right sometime around eight minutes, the potatoes, I mean.

G: Yep. With a rotating tray, that’s exactly right.

Total will land around 15–17 minutes. If one’s still firm in the center, give just that one 30–60 seconds more.

回（まわ）る 皿（さら） が ある。— There is a rotating plate.

M: Cooking chemistry question. Why is it that the Pam I sprayed the muffin tin with turns dark or even black when it's not connected with anything cooking, but doesn't appear to actually have any kind of discoloration when it's on or being attached to or somehow involved with one of the meatloaf muffins?

G: Short answer: the oil is overheating and oxidizing when it’s bare, but it’s thermally protected when it’s in contact with food.

Longer, chemistry-level version:

What PAM actually is

PAM is mostly:

That oil has a smoke point that’s lower than people expect once it’s spread into a micron-thin film.

Why bare PAM turns dark/black

When the spray is:

…it can easily exceed its stable temperature locally. What happens:

  1. Oxidation – oxygen + hot oil = polymerization
  2. Pyrolysis – the oil partially breaks down
  3. Carbonization – what you’re seeing as brown → black varnish

This is basically the early stages of seasoning, except uncontrolled and ugly.

Thin oil + hot metal + oxygen = burnt residue.

Why it doesn’t darken under the meatloaf

When the oil is touching food:

So the oil:

In other words:
Food acts as a heat sink and oxygen barrier.

This is why you often see:

Practical takeaway

If you want to avoid that black residue:

油（あぶら） は 空気（くうき） と 熱（ねつ） で 焦（こ）げる。— Oil burns when exposed to heat and air.

That’s the whole phenomenon, no mystery.

M: Less worried and more just curious. I mean, it seems to be working fine. So, it should be safe. But, you know, stuff that acts differently in different situations makes someone's curious.

G: Totally fair curiosity. This is one of those places where the same substance behaves very differently depending on context, and cooking is full of that kind of “wait, why?” moment.

A clean way to think about it:

Same oil, different environment

The oil isn’t changing its identity — the conditions are.

Bare metal + air

Oil + food

So what looks like “acting differently” is really different failure modes being enabled or prevented.

Why your intuition is right that it’s safe

If it were dangerous, you’d see:

You didn’t, because the oil under the food never hit those conditions.

The deeper cooking-chemistry principle

Water is a thermal governor.
As long as water is present, a lot of scary chemistry simply can’t happen.

That’s why:

Once moisture is gone, then reactions accelerate fast.

物（もの） は 条件（じょうけん） で 振（ふ）る 舞（ま）う。— Things behave according to conditions.

Your curiosity is exactly on target here.