The Rockbridge Bloomery – Reports

 

The Little Princess Bloomery

A Preliminary Report

Skip Williams  - May 2, 2006

 

 

Since January 2005, Lee Sauder and I have participated in approximately 30 iron smelts all using variations of the Coated-Tyle Bloomery described on other pages on this site. Drawing on this experience, we have designed and operated a simple clay-built bloomery with spectacular results, and developed a set of construction techniques, and operating parameters that work well with a clay shaft.

 

Construction

The Little Princess in built with a mixture of new, reused, and recycled materials that are now familiar to everyone who has ever built a bloomery before.

 

To build the shaft you will need:

-The remains of a previously fired bloomery, crushed to sand and grit sized particles. This is the grog. If this is your first furnace you can use sand as your grog material.

-An equal volume of charcoal fines. Screened through a ¼” mesh.

-A 50 lb bag of ball clay.

 

Mix the grog, charcoal, and half of the clay while dry. Add water and more ball clay as needed to make a stiff plastic mixture.

 

 

 

Text Box: The Little Princess BloomeryThe shaft is built up around an internal form (wood or sheet metal) which is removed at the end of construction. At the bottom of the furnace the wall is approximately 5” and tapers to 2” thick at the top. When you have completed building the shaft carve a small air inlet near the bottom where the tap arch will be, and start a fire burning. The shaft will be bone dry and ready to use in about 5 hours.

 

Dimensions

Internal Diameter 25cm (10in.)

Total Height 90cm

Tuyere to Top 70cm

Tuyere to Tap Arch  10cm

 

Operation

This furnace is run in the same manner as the Coated-Tyle furnace mentioned above.

 

 

Experiment 83

Charge Interval 8 minutes

Total ore 45 lbs.

4 hours 20 minutes from first ore charge to bloom removal.

 

Bloom weight 13 lbs.

Bar Weight 11 lbs.

 

 

 

 

 

 

 

 

Anchony from Experiment 83
 
 

 

 

 

 

 

 

 

 


Experiment 84

Charge Interval 10 minutes

Total ore 45 lbs.

4 hours 20 minutes from first ore charge to bloom removal.

 

Bloom weight 18 lbs.

 

During the first smelt in the little princess bloomery (smelt 83) the furnace walls vitrified and the whole mass became one solid piece. The next week we were scheduled to run a demonstration smelt for Evelyne Godfrey at the University of Mary Washington, so we picked up the furnace and loaded it into the back of the truck along with all of the other Text Box: Split bloom from Experiment 84smelter's tools and headed out to Fredericksburg about 3 hours drive away. Once there, we set the furnace back down on a plinth built of bricks and blocks filled with charcoal fines. Everything went according to plans (how often does that happen?) and after a few hours of tending the furnace we pulled out a nice bloom.

 

Morgan Riley in the Dept. of Historic Preservation at the University of Mary Washington has put together a presentation that will give you a better idea of the experience than the few meager words that I can put on a web page. You will find it at: http://departments.umw.edu/hipr/www/MW_Smelt1.ppt (warning 47 Mbytes)

 

 

 

 

Our special thanks go to many of you who have added ideas to this design, Jake Keen in the UK and the researchers at the Pre-Historic Open-Air Museum in Eindhoven (NL), Thijs van de Mannaker and Roeland Paardekooper, who were already pushing this field forward long before we entered it. I also want to include in this list Hermann Drexler of the Sachsenhof Museum in Greven (DE) who makes as nice a bloom as you can ask for.

 

----