Stone Whorl for Danish Viking Spindle

Grazia Morgano

1 February AS XLVIII

Abstract

This is a stone spindle whorl, based on the finds at Hedeby, inDenmark. It has all dimensions and the weight in keeping with thosereported by Eva Andersson’s analysis of the whorls that were found. Interms of physics, its spin should match that of a period Hedeby whorl,because its moment of inertia falls near the mean of the bell curvefound by Verhecken’s analysis. The moment of inertia determines howreadily an object begins rotation or ceases rotation, thus determininghow quickly and how long a given spindle will spin. The moment ofinertia of a given spindle does change over time as the spindle fillswith yarn, increasing the mass and therefore the momentum.

The whorl was created using modern mass-produced tools, thoughboth drills and hack saws are known in Viking Scandinavia. This tech-nique for making a stone whorl was demonstrated to me by MasterBedwyr Danwyn at Fabric, Fiber, Fighting, and Fencing in Æthelmearc.

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Contents

List of Figures 3

1 Hedeby’s Spindle Whorls 41.1 Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.2 Stone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3 Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Reconstruction 72.1 Making the Whorl . . . . . . . . . . . . . . . . . . . . . . . . 72.2 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.3 Final stats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3 Conclusion 13

Bibliography 14

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List of Figures

1.1 Andersson’s distribution graph of whorl diameters and weights 41.2 Verhecken’s histogram of moments of inertia at Hedeby(Verhecken,

2010, p. 259) . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1 Preparing the stone for cutting . . . . . . . . . . . . . . . . . 7a The back of the stone is smoothed out . . . . . . . . . 7b A guiding circle is carved into the stone . . . . . . . . 7

2.2 Creating the center hole for the spindle shaft . . . . . . . . . . 8a Drilling a hole in the center of the circle. A small

square was used to ensure the hole is perpendicular tothe surface of the tile . . . . . . . . . . . . . . . . . . . 8

b A quarter inch hole . . . . . . . . . . . . . . . . . . . . 8c Tapering the hole using a tapered reamer . . . . . . . . 8

2.3 Cutting the circle . . . . . . . . . . . . . . . . . . . . . . . . . 9a Using a hack saw to cut tangential to the circle markings 9b Hacksaws are known in period, from the Mastermyr

find (Arwidsson and Berg, 2000, plate 22) . . . . . . . 9c An octagon is the first step toward a circle . . . . . . . 9

2.4 The finished whorl . . . . . . . . . . . . . . . . . . . . . . . . 92.5 Yarn spun with the whorl . . . . . . . . . . . . . . . . . . . . 112.6 The green dot shows where this whorl lands, adapted from

Andersson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.7 The green line shows where this spindle weight’s MI falls,

adapted from Verhecken . . . . . . . . . . . . . . . . . . . . . 12

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1. Hedeby’s Spindle Whorls

1.1 Dimensions

At Hedeby, 939 spindle whorls were recorded. Most, 88%, are ceramic, 6%are bone, 4% are stone, and the remainder are various other materials, in-cluding amber and wood. Two thirds of the stone whorls found are flat discs.The remainder are convex. Looking only at the stone whorls, the masses fallwithin the range of 4–75g, though the largest part of the distribution curveis 10–25g. The diameters range 20–75mm, but the largest part of the distri-bution curve is 25–40mm. Thicknesses of all whorls vary 5–45mm, includingthe thick, conical ceramic whorls (Andersson, 2003, p. 118-119). See Figure1.1 for the distribution of weights and diameters.

Figure 1.1: Andersson’s distribution graph of whorl diameters and weights

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1.2 Stone

While no information is given regarding what types of stone were used in theHedeby whorls, the stone whorls found at Birka include sandstone, limestone,slate, soapstone, quartz, quartzite, and imatra (Andersson, 2003, p. 74–75).

1.3 Physics

The spindle whorl’s mass, width, and distance of the concentration of massfrom the axis of rotation (the spindle shaft) all affect the resulting yarn. Whatthey affect overall is the moment of inertia–the willingness of a rotationalbody to begin to rotate. This affects how much torque needs to be appliedto start the spinning, how quickly it spins, and how long it will continuespinning.

The moment of inertia can be calculated for a flat cylindrical whorl usingthe equation MI = m

8D2. However, a hole does have to be drilled in the whorl

for it to fit on a spindle, which affects the calculation, since a small amountof mass is further from center than it would be if solid. A revised equationis MI = m

8(D2 + d2) where D is the outer diameter in centimeters, d is the

diameter of the hole in centimeters, and m is the mass in grams(Verhecken,2010, p. 262).

The moment of inertia and mass together affect the yarn produced andthe process of spinning. While it is commonly said that a lightweight spindlefavors thin yarn and a heavier spindle favors thick yarn, this is more todo with thinner yarns having lower tensile strength, the reason supportedspindles exist. The spindle’s RPMs and length of time spent spinning areaffected by the moment of inertia, but the thickness of the yarn is determinedmore by the fiber and the spinner (Verhecken, 2010, p. 268).

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Figure 1.2: Verhecken’s histogram of moments of inertia at Hedeby(Verhecken,2010, p. 259)

2. Reconstruction

2.1 Making the Whorl

The stone used was a 2” square piece of slate tile from Home Depot, about6mm thick. The tile was sold in a package of 25 with a backing holdingthem together for easy grouting. After removing the tile from the backing,a cross-hatch pattern of glue residue was left on the back. A rasp was usedto remove this residue and smooth out the back of the tile (see Figure 2.1a),and then a compass was used to mark a circle of 17mm radius. The compasswas held so the sharp metal end carved the circle into the stone, rather thandrawing with the pencil (see Figure 2.1b).

(a) The back of thestone is smoothed out

(b) A guiding circle iscarved into the stone

Figure 2.1: Preparing the stone for cutting

Next, a series of drill bits were used to drill a progressively larger hole(18”, 3

16”, then 1

4”) through the center of the circle. This was done using a

hand drill, because they are low-vibration and do not risk breaking the stone(see Figure 2.2a). Viking age drills used spoon bits and were operated witha T-shaped handle (Arwidsson and Berg, 2000, p. 35). The hole was made

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inch across (see Figure 2.2b). Then the hole was tapered using a taperedreamer (see Figure 2.2c). A tapered shaft is advantageous for fast spinning,as the narrow diameter at the end of the shaft produces more RPMs withfinger-flicking (Verhecken, 2010, p. 265). The tapered hole corresponds tothe taper on the spindle shaft. If a straight hole is used, and the shaft’swood expands in summer’s high humidity, it may be impossible to get thewhorl onto the shaft. Similarly, if the shaft’s wood contracts in winter’s lowhumidity, the whorl may fall off. With a tapered shaft, the only changewith temperature is how far onto the shaft the whorl goes. The taperedhole ensures that there is significant surface area contact so that friction caneasily keep the whorl in place.

(a) Drilling a hole inthe center of the cir-cle. A small square wasused to ensure the holeis perpendicular to thesurface of the tile

(b) A quarter inch hole (c) Tapering the holeusing a tapered reamer

Figure 2.2: Creating the center hole for the spindle shaft

The circle was then cut from the square stone. A vice (lined in soft wood,for cushioning) was used to hold the stone still while a hack saw cut awayeverything that is not the whorl (see Figure 2.3a). A series of straight cutswere used to create first an octagon (see Figure2.3c), then a rounder shape.

Finally, the edges of the whorl were filed smooth. The spindle was puton the shaft and tested for wobble then filed until the shaft spun true.

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(a) Using a hack sawto cut tangential to thecircle markings

(b) Hacksaws areknown in period, fromthe Mastermyr find(Arwidsson and Berg,2000, plate 22)

(c) An octagon is thefirst step toward a cir-cle

Figure 2.3: Cutting the circle

Figure 2.4: The finished whorl

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2.2 Testing

The whorl was tested by spinning Icelandic yarn. Due to the relatively lowmoment of inertia, the spindle spins quickly, while its low mass means it haslittle momentum and does not spin very long. It is possible to draft1 onlyonce or twice before the spindle ceases its rotation and backspins.

It is important to note that the mass of the spindle overall changes asyarn is produced, because it is wound around the spindle. As mass increases,so does the rotational momentum. When nearly 100g had amassed on thespindle, it was possible to draft two or three times before the spindle lostmomentum.

Using Icelandic wool, this meant about a foot of yarn could be producedper spin, and the resulting yarn is 24 wraps per inch—lace weight, appro-priate for weaving a medium-weight fabric. Using a spindle of the typecommonly available in yarn shops, with a larger, heavier wooden whorl, Ican spin several feet of yarn with each finger-flick of the spindle.

While Verhecken’s report of an experiment conducted using different spin-dle moments of inertia, different fibers, and different spinners shows there isnot a direct correlation between the moment of inertia and the yarn produced,the ease with which different weights of yarn are produced is not discussed(Verhecken, 2010, p. 268). My experience with commercially available spin-dles shows this weight of yarn is more difficult (though not at all impossible)to achieve with the types of spindles most commonly available today, whichhave larger, heavier whorls. Lace weight spindles are commercially available,but they are far less common than they were in period, based on the analysesby Andersson and Verhecken, which show such low-weight, low-MI spindlesas being the common case.

1drawing out fibers, feeding them toward the spindle

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Figure 2.5: Yarn spun with the whorl

2.3 Final stats

The final whorl is 34mm diameter and 16g—within the 25–40mm commonrange of whorl sizes from Hedeby.

The center hole is 14

inch. That is slightly over 6mm, in line with the6–8mm hole sizes from Hedeby.

The mass is 16g—falling in the middle of the 10–25g common range ofmasses found at Hedeby.

The whorl is 6mm thick—within the range of 5–45mm found at Hedeby,though obviously on the thinner side of it. The thicknesses given in thereport do not distinguish between the discoid stone whorls and the sphericalor conical ceramic whorls, though. Given the diameters and masses involved,it seems likely that the stone whorls were on the thinner end.

The moment of inertia is 24 g cm2, middle-of-the-pack for Andre Ver-hecken’s statistical analysis of the moments of inertia for the Hedeby spin-dles(Verhecken, 2010, p. 259). See Figure 2.7.

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Figure 2.6: The green dot shows where this whorl lands, adapted from Andersson

Figure 2.7: The green line shows where this spindle weight’s MI falls, adaptedfrom Verhecken

3. Conclusion

Further work could be done with creating other whorls in different parts of thedistribution curves and comparing their resulting yarns and the experienceof spinning with them.

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Bibliography

Eva Andersson. Tools for Textile Production from Birka and Hedeby. Birkaproject for Riksantikvarieambetet, 2003. ISBN 9172092955.

G. Arwidsson and G. Berg. The Mastermyr Find: A Viking Age Tool Chestfrom Gotland. Larson Publishing Company, 2000. ISBN 9780965075510.URL http://books.google.com/books?id=M6u_AAAACAAJ.

Andre Verhecken. The moment of inertia: a parameter for the functionalclassification of worldwide spindle-whorls from all periods. In NESAT X(Northern European Symposium on Archaeological Textiles 10), 2010.

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