Making Authentic Caligae
Valkenburg/Castleford Caliga
Cutting Pattern for the Valkenburg/Castleford Caliga
A variant of the Mainz Caliga
To make authentic caligae one must first find an authentic cutting pattern.  Above is illustrated the best that I've so far located, taken from the book, "Stepping Through Time", the cutting pattern for the so-called Valkenburg/Castleford caliga and a pattern that I made for the Mainz variant.  Click on the following link for an example of the Mainz variant: Mainz.  More illustrations of caligae from Mainz may be seen in "Roman Military Equipment", by Bishop and Coulston.  All caligae found are notable for their narrow straps.  This pattern also has narrow straps going between the toes.  Single toe straps are shown in the Bishop and Coulston book.  The number of ankle straps varied from one to three.  Michel Feugere shows a few of the possible variations on page 179 of his book, "Weapons of the Romans".  More information on the construction of roman shoes may be found here.

I've recently acquired a couple more caligae references.  The Valkenburg style is described in the book, "Romeins lederwerk uit Valkenburg Z.  H.".  The book is in dutch, but there are plenty of photos and drawings.  The nailing patterns were much more varied than what I have been using.  "Romische Lederfunde aus Mainz" shows both caligae and calcei finds from Mainz.  This book has helped me to understand the unique lacing of the Mainz style.  Though I drew my pattern with single straps about the toe, as is shown in Bishop and Coulston, V shaped toe straps were perhaps more common.

I've just started the construction of yet another pair of caligae.  This time I spent more time on the pattern.  I finally got around to trying the duck tape over the feet method as described by
Florentius.   While I did not use his method to make an entirely new pattern, this technique provides a very good way of checking the existing pattern.  For my feet an upward curve of the lowest ankle strapes was definitely indicated.  Here is my new pattern:
My New Caliga Pattern
Changes in my new caligae construction include:

1.  Use of thicker leather for the upper.  Those located in Europe have the advantage of being able to see close up the genuine article.  It is the opinion of those who appear to be more familiar with this topic than I am that the leather of the upper should be in the 3mm to 4mm thick range.  My next caligae will therefore use 8-9oz leather instead of 5-6oz.

2.  I am going to try Martin Moser's method of stitching the lower back.  Stitching together the "keystone", as shown on the original pattern left much too much material behind the heel.

3.  Instead of two pieces of 8oz leather glued together to make the outsole I am going to use a single piece of 16oz bends.  This is specially compressed leather designed for such an application.  This is also more correct as I am told that the calligae found have only a single piece of leather making the outsole.

4.  The use of real hobnails.

Roman footwear is also notable for the use of nails to attach the soles.  Below is a common nailing pattern that the Romans used.  Notice the similarity to that of a modern running shoe!
Nailing Pattern
Valkenburg Nailing Pattern
My Hobnails from Matt Luke have arrived!  The difference between them and the Tremont nails, and the Le Prevo nails is quite noticable (Tremont on the left followed by the Le Prevo hobnails, with Matt Luke's hobnails rightmost):
The progression of improvement is quite noticable.  Though still not quite right, the Le Prevo hobnails look much more like real roman hobnails.  The downside is that they are cast steel not forged.  In contrast, those from Matt Lukes are spot on.
In the cutting pattern I high-lighted certain parts in color.  Keep in mine this is from my experience fitting caligae to my feet, what works for your feet may be different.  As drawn, the pattern is too wide for my feet.  I've high-lighted in blue where I made the heel section of the sole narrower.  Caligae should fit tight about the foot.  If you have wider feet then the pattern may be just fine as it is.
The outside straps are drawn much too long.  This may be remedied by simply delaying the cutting of the strap holes to last.  Cutouts that should be done last I've high-lighted in red.
To make sure that the straps come out long enough, I've shown in green where the straps should be initially cut longer.
The first pair of caligae that I made from pattern from "Stepping through time" resulted in shoes with too much material behind the heel.  For the new pattern I changed the back.  Notice that the notch is gone.  The idea is now to simply fold the leather around the back of the heel
First print out the pattern.  Then measure the length of your longest foot from the base of the heel to the tip of your big toe.  The ratio of this measurement to the corresponding length of the printed pattern gives the required magnification factor.  Most copy centers have machines that can make enlargements from magnification factors taken to two decimal places.  This gives a cutting pattern scaled to your feet.
From the bends cut out the out-soles.  Make sure to do a left and a right!  From the 5-6oz leather cut out the insoles.  Some people make the insoles a bit smaller than the out-soles.  I found that making them the same size worked find.
From 8-9oz leather cut-out the uppers.  Make sure that you cut a left and a right.  Do not cut the red cutouts!  Play particular attention to the little semi-circular knobs at the joins between horizontal and vertical straps.  Is it my opinion that these are not just decorative, but serve to prevent the tearing of the thin straps.  To make these use a 1/8 inch round wood carving tool, carefully working your way around the circumference of the knob. Use an edge beveler to round the inside edges of the straps.
Next stitch together the backs.  Many types of stitches are possible, a simple cross stitch is particularly easy to do, but this does not seem to be what the Romans preferred.  An edge stitch, reinforced by a tacked-on strip of thin leather, appears to been very common:
Back Seam
Edge Stitch for the Back Seam
If your particularly anal you could do both sides.  With the added reinforcing strips having the edge stitch on just the outside appears to be sufficient.  The reinforcing strips are applied using a simple running stitch, on both sides, over the edge seam.Notice now that after stitching together the backs you're left with a small opening on the bottom.  There has been some conjecture as to what to do here.  Leave it open or stitch it closed?  I prefer to have the backs of my caligae closed.  Fold the leather around the curved back, trim of any excess, and attach using a whip stitch.  I did not do exactly as Martin did, the leather seemed to be a bit too stiff, but simply stitching the back to the rounded part of the middle layer seemed to do the trick.

I no longer recommend simply glueing the out-sole.  While the in-sole may be safely glued in-place, glue by itself, even with hobnails,  is not sufficient to keep the out-sole attached to the upper.  The out-sole needs to be stitched on using either a tunnel stitch about the edge, the hard way, or by a tunnel stitch between the upper surface of the out-sole and the upper, the easier way.  Using a curved awl make a series of tunnels in the out-sole following the edge.   An 1/8 inch from the edge is likely a good choice.   As the stitches in the upper will be covered by the in-sole a simple tack stitch is fine there.  When sewing, use a flexible needle to run the thread through a tunnel, up and down through the upper, and continue until you have the entire stitch completed.  You may want to go through a few iterations tighting up the thread till the upper and out-sole assembly is secure.  See below for details on the required tools.  When glueing in the in-sole use spring clamps to hold everything together.  The outsole, upper, and insole form a sandwich through which the nails are inserted. 

Following the nailing pattern pound in the hobnails.  Roman reenactors in the USA have been using 5/8 inch Tremont Cut Nails. Though of the right diameter and much better than say carpet tacks, they look nothing like roman hobnails.  Roman hobnails are conical in shape.  Recently I discovered a source of almost correct hobnails from
Le Prevo Leathers in the UK.  My current pair of caligae use these.  To apply the nails first draw the nailing pattern on the bottom of the outsole in pencil.  I found that the guide holes that were necessary when using the Tremont cut nails was no longer required. The irregular cross section of the Tremont nails tends to cause them to bend in unexpected directions.  You need some sort of anvil to pound on.  There has been quite a debate on clinching of the nails.  Previously I was definitely in the clinching camp, but now I'm not sure.  Roman caligae consisted of only three layers, the out-sole, the upper, and an insole.  Walking on clinched nail ends is not particularly comfortable.  The Le Prevo hobnails come with shorter shanks.  Using the layers of leather that I did, 6mm out-sole, 3mm upper, and 2mm insole, gave plenty of room for the nails.  The nail shank just poked into the insole without penetrating it.

Having forgone clinching of the nails, some additional means of attachment is a good idea.  On the pair of caligae shown below I additional bit of security is provided by a zig-zag tunnel stitch on the outside between the out-sole and the upper.  Due to the hardness of the bends this is not an easy operation.  I did this about both the heel and the toe.  Curved awls and either curved or flexible needles are needed.  Flexible steel needles, formed by a piece of thin steel wire folded over into a loop and solder at one end are used to sitich through the tunnels.

We're almost done.  Put your feet in your new caligae and pinch the straps together.  Mark with a pencil the location where they join together.  This will tell you how long the straps need to be and where the lacing holes need to be.  Trim the straps and finish cutting the holes.
Finally, finish the leather with a generous coating of Neatsfoot oil.
Caligae are laced in a criss-crossed pattern.  Start by threading the leather lace from the outside of the two outer-most straps at the toes.  The straps at the toes are an exception.  Notice that there is one strap on the inside for four straps on the outside.  Just bunch these four outside straps together against the single inside strap.  Then simply criss-cross the lace going from strap to strap making tight Xs between the straps.  Tie the lace about your ankle as you would any shoe.  Be careful when purchasing the lace.  Tandy appears to sell lace in at least two thicknesses.  You want to use the larger lace that is about 1/8 inch by 1/8 inch square.

When you're done you should have a pair of caligae like these:
My new caligae on my feet
My latest Caliga
Front view
My latest Caligae
Here is a view of the bottom showing the Le Prevo hobnails:
Here is a vew of the back seam:
Back view
After Action Report
I wore these caligae to the recent Fort Malden roman event in Canada.  Overall they worked out quite well. Like any new pair of shoes the leather has stretched out a little bit making them somewhat more comfortable to wear.  Two issues though:

1.  Some of the out-side tunnel stitching got cut.  I had to redo this.  It appears that I had placed some of the stitching too high on the upper  above the sole.  These need to made as close to the sole as possible.  Further use does not seem to show any more problems.

2.  The lower tabs going about the feet tended to slide back and forth.  I fixed this by replacing the laces with longer ones and wrapping the lace around the tabs to secure them.  Comfort seems to be improved as well.  See the photo below:
Old construction
New construction
New construction: sole 1/8 inch longer than in-sole
Old construction: soles equal length
I recently rebuilt these caligae by replaceing the soles.  Not only is the new sole attached using a layer to layer tunnel stitch, but I've made the sole 1/8 inch longer in the back.  This should avoid the bulged-out look that I had been getting when using soles of equal length.

I'm also not sure about wrapping the lace around the tabs.  I've found that it is very difficult to tighten the lace after wrapping   A simple zip-zag might be the best method after all.
Required Materials
One double shoulder 8-9oz (about 3mm thick) tooling leather is good for a couple of pairs of caligae.
One 16oz (6mm thick) bend for the out-soles
one 5-6oz (2mm thick) shoulder for the insoles, and
one 2-3oz  (1mm thick or less) for the back reinforcement.
Waxed linen thread.  Recently on Roman Army Talk, RAT, there was described an alternative to waxed thread, coating the thread with something called "shoe-maker's pitch".  I'm told that this stuff is available in Germany, but since I have not been able to locate a supply of it here in the states, I cannot say which is better, waxed or pitched thread.
Though carpender's glue would work, I now prefer E6000 (it's also waterproof).  You'll find it at art supply stores.

Leather stitching is typically done with blunt needles.  Thread holes are made with a scratch awl.  Tandy leather has these.
Tunnel stitches usually require a
cuved awl to make the holes and either cured needles or flexible needles.  I'm told that pig's bristles work as well.
Sharp knives to cut the leather.  I like to use an x-acto number 2 blade.
As described earlier, a 1/8 inch round wood craving tool makes short work out of cutting the knobs in the uppers.
Some spring clamps.
A 16oz hammer and an anvil.  I recently acquired a
shoe-maker's anvil from RLQM.  It is supported by the Hardy hole in my large 110lb anvil, but could just as well be supported by a vise.

Here is a picture of my leather working tool set
My leather working tools
I recently made a change to my construction.  Instead of glueing the out-sole and tunnel stitching about the edge I now employ a tunnel stitch between the upper and the out-sole surfaces.  A pre-exquiste is the need to soak the out-sole in warm water for a couple of hours.  At first I attempted the making of the tunnels in the out-sole using curved awls.  After breaking every curved awl in my possession, I switched over to a cut-off curved suture needle.  It turned out the this worked much better and I have yet to break one of these.  I simply cut-off the eye and chucked the curved needle into an awl holder.  The fabrication using tunnel stitching between the surfaces of the upper and the out-sole is not only easier than tunnel stitching about the edge, a firmer construction is made.

The construction method using tunnel stitching is illustrated below:
Sole Construction using Tunnel Stitching
Curved Awl for making tunnel stitches
Once the tunnels in the out-sole have been made the sewing itself is easier to do using flexible steel needles.  Martin Moser sent some of these to me, as I've been unable to locate a source of supply.  These should be easy to make as they consist of a peice of thin steel wire, about 26 gauge, folded over into a loop and soldered at one end.

Here are a pair of caligae that I recently made for a friend.  These have the out-soles attached to the uppers using the method of tunnel stitching previously described.
Making the Mainz Caligae
I've just started the process of building a pair of Mainz variant caligae.  I like to transfer the paper pattern to heavier card stock to make a final template:
The primary difference between the Valkenburg/Castleford variant that I previous made and the Mainz is that all of the toe and side straps come together at a single point located about a third of the way from the front.  The heel straps and ankle straps come together as they did with the other form.

Here is one of the uppers cut out.  Always mark the pattern cutouts on the flesh side in pencil.  To make the cuts I prefer a #2 xacto blade.  Here I am smoothing the edges of the flesh side using an Osborn TL-127 #4 edge beveler.  Why round the edges?  That's what the romans did.
Rounding the strap edges
Having finished the preliminary cutting out and edge rounding of the uppers, the next step is to prepare the backs for stitching.  First oil the leather.  You may skip oiling the outsoles for now.  First mark the stitch holes every 1/4 inch on a line located about 1/8 inch from the edge.  Then holding the straight awl at about a 45 degree angle carefully make holes from the grain side through the edge.
Having made the stitch holes, the next step is to stitch the back together.  Here I am using a flexible needle to make the edge seam.  Some people do this with a needle on each end of the thread, a double needle stitch.  I achieve identical results by simply going back to the top from the bottom.
The completed back seam ( I only broke through once, no matter, this is all going to get covered up):
The bottom is stitched together using a simple cross-stitch.  Next, the reinforcement strip.  Not only does it reinforce the back seam the stitches closing the bottom are also protected.  This is a high wear area and without the reinforcement strip you risk having your caligae come apart.  A simple running stitch is sufficient here.
Now it is time to stitch on the out-sole.  First mark out where the tunnel stitches are to be located and trace the outline of the sole on the upper.  Draw a line about 1/8 inch in from the sole edge and make a mark every 1/4 inch.  Then soak the sole for at least a couple of hours in hot water.  Using the curved suture needle make the tunnels.  I usually make these about 1/2 inch to 3/4 inches long.  Attaching the sole to the upper then proceeds as I have shown in the previous drawing, down through the upper, throught a tunnel, and back up through the upper.  Do this along the entire circumference of the sole.
With the back done, the sole sitiched on the caliga is ready for nails.
As the shank of the hobnails was a bit too short to be clinched, I went ahead and glued-in the in-sole before doing the nailing.  For an adhesive I used Barge Cement.  Draw the nailing pattern in pencil prior to the actual nailing.  Another change from how I did things previously was to make the out-sole about 1/8 inch longer than the in-sole.  With the sole extending further back the bulged-out heel look should be avoided.  Here the finished nail pattern:
The last step is to adjust the length of the straps and touch up on the Neats-foot oil.  This boot may be laced in a number of ways.  I have simply threaded each of the toe straps on one end of lace so that they all meet at the same point.  Loop the lace in a zip-zag fashion to bring the heel and ankle straps together and tie as you would any shoe.
The finsihed caliga
Here are the pair of finished boots.  I decided to double-up the in-sole as the hob nails were a bit long.  The socks with cut-outs for both the heel and toes come from the Cancelleria Relief.
I've just received the book, "Romische lederfunde aus Mainz".  I cannot read it, but it has lots of pictures of caligae.  Based upon one of the drawings, I relaced the caligae, instead of having all of the toe straps on one side of the lace I now alternate them on both sides, and made a few more adjustments to the straps, punching additional holes to shorten the effective length of the straps.  I managed to remove the large gap that I previously had about the toe:
One more pass at adjusting the toe straps.  I shortened some of them.  This is pretty much the final form of these boots.
Final form
A word about the lacing.  As far as I know, no caliga has been found in its fully laced form.  We are forced to perform a bit of speculation here.  The final form of lacing used here is suggested from a drawing in the Romische Lederfunde aus Mainz book and it certainly works.  Basically they show the left toe straps laced on the left and the right toe straps laced on the right.  I varied this arrangement a bit by lacing some of the right toe straps to the left lace and left toe straps to the right lace.  The opposite lace then passes through the V of the strap.  How I did this was simply a consequence of how I cut the toe straps.  Bottom line some experimentation is needed to find the best arrangement.

Here is a comparison of the two styles of caligae:
Mainz Caligae
Valkenburg Caligae
Making the Pattern
I've been thinking about what information needs to be provided to make a well fitting pattern for caligae.  I've concluded that besides the insole outline, which provides a magnification factor for enlarging the basic pattern, some three dimensional information on the wearer's feet is also needed.  Sufficient information may be provided by the construction of a duck tape model.  See the Florentius site for a description of the process.  Having wrapped your foot in duck tape make two lines, one showing the back seam and a second showing the top center line where the straps meet:
Carefully cut the duck tape from your foot along the marked lines.  With the duck tape laid flat you can tell how to adjust the straps.  My insole pattern is shown below.  It is likely best that you make your own insole pattern.  I have a narrow heel and the pattern has been narrowed to fit me.  Also remember to make the outsole about 1/8 inch longer than the insole in the back.
My insole pattern
Here is the mock-up after removal from the foot.  Remember to include the insole cardboard as it helps to keep the shape.
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