Bellows Stone

Purpose: I am curious to see how a medieval refractory recipe stacks up against a modern refectory.

I have made side blast forges out of about 2 1/2 inches thick of castable hot top refractory and they seem to work just fine. While reading Theophilus' "On Divers Arts" i came across an instruction for making a forge. It read as follows.


Theophilus' "On Divers Arts"

The third book "The Art of the Metalworker"

Chapter 3. The Forge for the work

"... on the left hand side of a man sitting there should be set into the ground a wooden board three feet long, 2 feet wide, and almost 2 fingers thick. When this is firmly in place there should be a hole in the center, a finger in diameter and four fingers above ground level. There should also be a narrow piece of wood, four fingers wide and as long as the larger board, fitted to it in front

and fixed with wooden pegs. "... second board same size "so that between the two there should be a space of four fingers". Fill this 2/3 with fresh clay that has neither been kneaded or mixed with water and trim it smooth.

This is basically a big dang fireproof wall.

Then he says mix horse dung with kneaded clay and build up the forge and hearth poking a hole with a slender stick.

A nice text on bellows stones.

Goldsmithing & Silver Work: Jewelry, Vessels & Ornaments By Carles Codina

States that crucibles are made for the Ashanti method by mixing 45% horse manure, 45% potters clay, and 10% charnotte(refractory clay)


1) Period sizing schmizing. I've seen m fires and I know this will be a portable occaisional forge for me.

2) This is partially because I want to see how well this refractory holds up.

3) Theophilus was NOT describing how to make a portable forge.

4) this may just crack and explode on me the first time

6)The bellows I made are probably way oversized for this but It'll be fun to see how well this works.

7)THIS IS ME SLAPPING TOGETHER TWO TIME PERIODS. A scandinavian bellows stone meets an elizabethan side blast forge you will see metal ones like this showing up during the revolutionary war. The design is simple. Something that doesn't burn or explode. A hole. And some dirt or sand. the next major improvement in side blast forges takes place in the 1800s with water cooled side blast forges that are still in use in europe today.

8)if I can find an 8x10 or larger piece of soap stone I need to try making a nice bellows stone.

9)If this works it will be worth it for the comedic value of the polished turd jokes. If this doesn't work it'll be a great anecdote. Never underestimate the value of humor during a historic demo.


1)take 50/50 dry horse poop and wet clay


2) smash the turds to break up the fibers and make sure the clay and the fibers mix


4)I built the bellows shield 4 fingers thick and set it to dry for a few weeks.


5) I smoothed it out a bit with a water dipped hand and relocated some of the clay from the sides to the top.

6) let her dry for a few weeks with a fan running

7) heat to 180F for four hours

8)heat to 220 for four hours.

9)heat to 450F for a few hours. and let cool.


The refractory seemed to hold up well under charcoal use but started to degrade when anthracite coal was used.

The bellows stone cracked due to an improper mounting of the bellows but that have me a glorious view of the inside of the material.

The results after antracite.