Create Astral: How to move less than 1 bucket of fluid?

I'm playing Create Astral. I'm trying to move less than 1 bucket worth of fluid (1 ingot worth of molten metal). Any suggestions how to do this?

The long explanation: I'm on Chapter 2 (Getting Industrial). I'm trying to complete the 'Efficient Bronze Production' quest. It tells me that if I throw copper and tin ingots into a mixer, I'll get double the output of bronze. Great! But it doesn't work... REI suggests that I need a Blaze Burner, super heated, for this. And for that I need Moon stuff...

But REI suggests that I can get molten bronze (I need a bucket to complete the quest) if I mix molten copper and molten tin in a mixer, no heating required. I toss a bucket of each in my mixer. It works! Except that it stops mixing at 888 mb of molten bronze, leaving 555 mb of both copper and tin, and I can't extract anything. So I try using pipes, a pump, and a fluid tank. That works, except when I break down the tank I lose the contents...

So I'm looking to toss a single ingot of both molten copper and tin in there to get that last 111 mb of molten bronze. And it seems that the Astral instructions are outdated...