'Boxed Bowl' (Vinland B)
Iron Smelting Experiment

Date: 25, 26 May, 2002
Place: Wareham Forge

On hand:
Darrell Markewitz (blacksmith)
Kevin Smith (archaeologist)
Neil Peterson
David Cox
Kevin Jarbeau
Gus Gissing
Michelle Smith
Steve Strang

loosely based on Norse / L'Anse aux Meadows 'incontinence' low shaft
Frame of stone slabs stood on edge, with local river clay sealing joints and forming lower bowl. Slabs backed up with dirt and sods.
17x15 on diagonals
15 depth
air blast enters at base level

Based on Norse 'double bag' type.

1. Ore from L'anse aux Meadows (mostly 1cm size) [FE03 6x% + SI] - 4.8 Kg
2. Forge scale (flake size 2-3mm) ["pure" FE03]

Roasting the ore
1. Two propane forges used
    a. Can - (average 15 minutes / batch) [460+ cm3 per batch]    
    b. Plate - (average 3 minutes / batch) [cm3 per batch]

Weight of roasted ore: 2.95 Kg
Two samples removed (28 g / sample)
Ore used in experiment: 2.9 Kg
The Ore was mixed with sand to increase the silicon content (9 parts ore, 1 part sand)

Furnace was originally heated with a wood fire (to dry/bake the clay caulking) beginning at 1225h
7 kg charcoal added at 1350hr to increase furnace heat and bellows pumping begun.
Original pump rate was 98/min reducing to 63/min inside pic @1428
A 3kg "ore" charge was added at 1441 and topped with 4 kg of charcoal     This "ore" was furnace scale and sand (mix) along with X kg of L'anse ore
Note that early charcoal additions are made when mass burned down by about 1/3.

From 1503 to 1511 there was no bellows pumping due to repair work being done on the bellows

A sample of the slag was removed using an iron rod at 1520

more charcoal @ 1544 - volume about 4 kg

Bellows stopped, 2nd charge added @ 1558 + 4kg charcoal, bellows resume

Decide to change pattern of charcoal additions  - with smaller amounts being added to 'top up'.  This appeared to retain more heat in the central mass.
more charcoal @ 1628 (1kg?)
more charcoal @ 1650 (1kg?)
more charcoal @ 1708 (1kg?)
more charcoal @ 1732 (1kg?)

3rd charge @ 1808 + 4kg charcoal

more charcoal @ 1835 (1kg?)
opened + inspected @ 1916 (photos) {interior is probed to determine existence of solid mass and its position}
bellows again @ 1921
more charcoal @ 1926 (0.5kg?)
bellows stop 2013

Furnace was broken open to examine while hot.

Allowed to cool overnight then sketched and fully pulled apart c. 0900h

total charcoal used: 22kg

Lower slag mass - total  8 lb 8 oz, consists of one piece (from lower left corner) at 1 lb 11oz of metallic (magnetic) slag plus main slag blob at 6 lb 11oz
1 lb slag removed from above bloom
1lb 4oz slag removed from front furnace rock above air hole
2 lb 2oz magnetic material from base ash (very small grain size)
 2lb 4oz non-magnetic material from base ash - Inc paper scraps

Air blast rates:
various hands on bellows, with variation on rate, force of pumping.
Average rate was about 65 - 70 pumps per minute
Kevin = 10 pumps 29L
Grim = 10 pumps 24L

Ore used
Part way through the smelt
the final slag bowl

Text and photography Darrell Markewitz