A Coffer of Oak and Gratitude

Several years ago my good friend, known in the SCA as Aelisia of Cambrewell, agreed to be my running-mate as candidates for the Baronage of Glymm Mere.  We were both ready for the job and capable for what lay ahead, but as I look back on the past three years I can confidently state that each success we had was due in great part to her wisdom, experience, and level head.

When we first learned that we had been selected to become the next Baron and Baroness, I had been planning on a personal project: a small coffer in the style of those extant examples from 14th century western Europe.  In other words, an oaken frame-and-panel coffer with linen-fold panels.  I had selected some 8/4 quarter-sawn white oak for the project, but had not gotten farther than stack-and-stickering it under my bed.  I decided that instead of making it for my own use I would give it to Aelisia at the end of our term of office.  I found plans for a coffer in Daniel Diehl and Mark Donnelly’s Constructing Medieval Furniture and promptly got to work on a lid.  Then the job started, and the project lay collecting dust for three years.

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Pieces cut to rough length and width.  These had lain untouched for several years until being dusted off in March 2017.  I refreshed the notes I had written on them in willow charcoal.  Below: The dry fit lid I made in 2014.

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In March 2017 I scheduled shop time for myself to begin this project in earnest.  Although several years ago I had constructed (but not finished) the lid using a combination of hand tools and power tools, I decided at this time to complete the chest using only hand tools.  My thoughts on this were several: to produce a work more historically accurate in appearance; to improve the depth and range of my woodworking skills; and, because this was a labor of great affection, I wanted to have a more personal connection with the creation.

The Research

Although the dimensions of the coffer were already dictated by the measurements of the lid I had begun (and the method of joinery was already established in the lid as well) I still had some flexibility in how to execute the body of the coffer.  In the time permitting I researched extant pieces and images of fourteenth and fifteenth century coffers, paying particular attention to: overall design; prevalence of mortise-and-tenon (as opposed to dovetail) joints; use of nails and dowels; applied decorative arts; and hardware.  I created a series of image files categorized by current location, geographic origin, era of creation, and primary materials.  If the piece was in a museum, I also noted the accession number for ease of finding it again.

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As I did not, at that time, have the thought of presenting to others my process on this piece, my research notes were later tossed out and are unavailable for inclusion here.

The research having been completed, I divided the work ahead into three stages: the rails and stiles; the panels; and finishing (smoothing, oiling, and waxing).

The Rails and Stiles

Rails and stiles are the framing members in frame-and-panel construction.  Rails run horizontally; stiles stand vertically.  In this coffer, the corner stiles would extend below the panels in order to double as the coffer’s legs.  The stiles and rails are “joined” (connected) in a method called mortise-and-tenon.  Tenons are (usually rectangular) tabs formed by reducing an area at one end of a stile or rail.  Mortises are holes of a corresponding shape to the tenon formed by boring and chiseling an area in the opposing rail or stile.  A tenon (tab) slides into the complementary mortise (hole) joining the rail and stile together.  Ideally, the fit should be snug (to prevent a weak and wobbly join) yet still allow for seasonal wood expansion.

I began work on the tenons of the top and bottom front rails and the front muntin (the stile separating the two front panels). The rails run horizontally and were to become the upper and lower frames of the two front panels. Their tenons would then slide into mortises set into the left and right corner stiles. The left and right corner stiles would be the left and right frames of the panels. The muntin would separate the two panels; its tenons would slide into mortises set into the upper and lower rails.

As I progressed on the coffer, I took more purposeful photographs than I have on past projects and even experimented with video recording myself at work.  I found this to be not merely distracting, but inherently artificial; my body position was never optimal for the work at hand when trying to accommodate a camera’s view.  My apologies in advance for the poor cinematography to which I will be subjecting you.

As you can see, I do not have a “proper” woodworker’s bench.  By which I mean that my bench does not have hold-downs and vices for securing work.  As with most of my tools, my bench is second-hand.  It is heavy and sturdy, and it serves me well, but it is not everything I desire it to be.

As I finished the tenons of each side of the coffer, I then turned to making the corresponding mortises.  To achieve as snug a fit as practicable, I transferred the dimensions of each tenon individually to the layout of the mortise into which it would fit.

Once the area to be mortised was defined by scribed lines, I bored out the majority of the waste with an auger.  To be sure I wouldn’t inadvertently bore too deep a hole I marked the auger with a piece of masking tape one inch from the end.  After using the auger, I squared the mortises corners and flattened the sides with chisels.
Each mortise required a little fine-tuning to get the fit right.  Once done, however, the joinery is tight without being jammed.  This is important, as throughout the process I had to disassemble and reassemble the coffer numerous times.  As I finished the tenons and mortises of each side (front, back, left, and right) of the coffer I laid them out and began indicating where the panels were to be inserted.

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So why “frame-and-panel” construction?  This method is much more labor-intensive than simply nailing, or even dovetailing, some boards together to make a box.  The advantage of frame-and-panel has to do with wood expansion and contraction.  All wood is subject to absorbing and releasing moisture.  This regularly occurs with the seasonal changes in moisture content of the air, and so is referred to as ‘seasonal expansion’.  Dry wood absorbs moisture from humid air; wet wood releases moisture to dry air.  As the wood absorbs moisture it swells (think of a dry sponge being dipped into water and subsequently doubling in size).  Where two pieces of wood abut each other and are each swelling they will crush their own fibers.  Conversely, as wood releases moisture it shrinks, causing joined pieces of wood to pull away from each other and rip fibers and joinery in the process.  Frame-and-panel construction makes allowances for seasonal expansion in several ways.  First, by having framing members with grain running both vertically and horizontally the overall direction of expansion (which is greater perpendicular to the grain than parallel to it) is spread more evenly across the construction.  Second, by having large sections (the panels) “float” unfixed inside grooves deep enough that the expanding wood will not crush itself, nor so shallow that shrinkage would allow the panels to fall out.  Third, by capitalizing on the simplicity and strength of the mortise-and-tenon joint; which makes allowances for seasonal expansion without sacrificing rigidity.

To insert the panels I had to rout grooves into the inside edges of the rails and stiles.  For the front and back rails, this meant the groove runs the entire length of each rail, passing through the mortises carved to house the tenons of the muntins.  For the corner stiles, this meant the groove runs only between the upper and lower mortises.  I had already laid out the scribe-lines for the grooves, so I grabbed my trusty combination plane, selected the right width of cutter, set the fence, and made quick work of the grooves on the rails and the center stiles.  When I turned to the corner stiles, however, a problem soon became apparent: as I was not cutting the grooves up the entire length of the stile, the plane’s skates quickly had trouble running off of -and onto- the uncut portions.

What to do?  I could auger out most of the waste and clean up the groove with chisels, but that seemed fraught with risk and unnecessary labor.  Digging through my tools looking for a solution I came across a hand router that had been collecting dust since I first brought it home.  The cutters were in sad shape as they apparently had been last sharpened free-hand on a grinding wheel.  I trued them on a diamond plate, then sharpened and honed them on a series of increasingly finer water stones until I got a mirror finish.

I installed a cutter of about the right width and set the depth-stop on the router.  Using it took some getting used to; it is surprisingly different than other planes.  There is a lot of freedom to move laterally (especially as mine does not have a fence) which is great for cleaning up wide expanses, but challenging for trying to groove a precise area.  The hand router doesn’t have much of a toe to speak of, so pressing down on the toe at the beginning of a pass (which is proper form for a bench plane) only serves to dig the cutter into the wood at a severe angle.  Lastly, because the sole of the router sits atop the surface not being planed, each pass requires the cutter to be dropped a little further.

If you are watching the video and thinking that I was struggling, you are correct.  After this video was shot I figured out how to fine-tune the depth-stop and avoid digging the cutter too deep.  Also, there was a knot.  Once I got the hang of the hand router, the grooves came along much easier.

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The Panels

After work on the frames was done I turned to the panels.  They had been rough-cut three years ago when I first started the project, but needed to be squared, flattened, and “raised”.  Raising a panel means to cut rabbets (called ‘rebates’ in England) along each of the sides and ends, creating a ‘step’ from a lower surface to a higher surface.

The panels were squared simply by scribing lines off of a square rule, then sawing down to the lines with a back-saw.  I flattened the panels first by using a scrub plane and following up with a jack plane and a smoothing plane.  A few minutes work with a card scraper brought the surface to a nice, smooth finish.

 

After rabbeting the sides and ends of each panel they slide nicely into the grooves carved into the rails and stiles.

Piece by piece the sides, front, and back of the coffer came together.

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Front of coffer; dry assembled.

Many of the extant coffers I have looked at have carved panels; usually just the front panels but often the sides too and even the back on occasion.  A widespread decorative style spanning from the 14th through the 16th centuries was linen-fold, a simple style of relief carving.

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A linen-fold coffer.  Metropolitan Museum of Art accession number 52.53.

As this coffer was to be a gift to someone often associated with vellum, parchment, and well-draped fabric, I wanted to incorporate linen-fold into the design.   I read up on the technique in Hasluck’s Manual of Traditional Woodcarving and found helpful on-line Youtube videos made by Mary May.  I sharpened my carving gauges and purchased a piece of white oak to practice upon.

The barony of Glymm Mere’s premier arts event, Lyceum, seemed to be a good time and place to learn something new.  So I packed the white oak board, some c-clamps, a combination plane, an assortment of moulding planes, a pencil, and a straight-edge, and a plan for doing a demonstration.

I began by clamping down the board and using the combination plane to cut rabbets on all four edges of the board.  Then I laid out long lines indicating the crests and troughs of the folds.  Next I sketched in the layered, folded ends of the linen.

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I turned back to the combination plane and plowed out the bottoms of the troughs and the background area along the sides.

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Setting a moulding plane into the groove I had just plowed, I started to give the trough more definition and curvature.  I had not had a lot of experience using moulding planes before and found setting the depth of the iron to be a challenge.  The iron is held in the throat by a simple wedge.  If the wedge is too loose, the iron will be driven back up the throat instead of cutting the wood.  Setting the wedge firmly into the throat, however, can cause it to carry the iron along with it, resulting in too much of the iron protruding from the mouth and a too-aggressive cut.  So I learned to hold the iron at the depth I wanted it, and the plane, and the wedge all in one hand while I pounded the wedge into place with a wooden mallet.

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Still, even with the iron finally satisfactorily set and the troughs plowed, the moulding plane was not as easy to use as I had anticipated.  It still tended to follow the curves of the grain when I wanted straight lines.  I also found that the sketches on the ends of the linen-folds were disappearing as I wasted out the troughs.  I re-sketched the folded ends and decided to work on those for a while (besides which, as a demo I wanted to show a variety of tools and techniques before I lost the attention of the group gathered around me).

 

By the end of the demo I had results to show for my efforts, but they were unsatisfactory.  The tools I had used were the right tools, but I was unpracticed.  I had enough success to be able to say “I can learn this” but I recognized that I am still a far distance from being able to say “I have learned this”.  I spoke with my friend Cristiana de Huntington and sought her advice in regards to this project.  With her counsel, I decided it is better to present a well-executed but less decorous piece to Aelisia than it would be to present a poorly-decorated piece.   I scrapped the idea of incorporating linen-fold into the project and prepared for the panels to be without decoration.

The Dowels

As I wished to make a coffer: consistent in execution with the extant examples I had found; able to last as long as the extant examples; and, able to be repaired as needed, I chose to pin the coffer together using dowels in lieu of nails.

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Detail of Metropolitan Museum’s coffer 21.89.1 showing heads of dowels used to pin tenon into mortise

To make the dowels (also called “treenails” or “trenails” in many documents) I began with scrap bits of white oak cut off while making this and other projects.  I looked for pieces six or more inches in length and as close to being just over 1/2″x1/2″ in cross-section as I could find.  Please note that I failed to photograph the making of the dowels for Aelisia’s coffer; the photos which follow are of the same process but were taken on another occasion.

I clamped the stock into a vice and used flat and hollow spoke shaves to make them roughly circular in cross-section.

Using a chisel, I then bevel the end of the stock slightly, just enough to fit it inside the circumference of the hole in my dowel plate.  If the stock is still to wide, I return to the hollow spoke shave and reduce the stock further.

My dowel plate is the base of an unmounted machinist’s vice.  I set it upside down with the vice clamps open fairly wide to make a stable surface.

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Then I simply pound the stock through one of the holes in the dowel plate.  The dowel plate performs two functions: it compresses the wood fibers which pass through it and it shaves off the excess stock that fails to compress into the hole.  The fibers will expand again as they absorb moisture.  I try to make the dowels just before they are needed, so that they expand inside the holes I’ve bored and do so when absorbing oil I have applied.  More on that anon.

The Assembly

With all of the pieces cut, shaped, smoothed, and fitted I was ready to put it all together.  The coffer had been dry-fitted already a number of times by now, so I knew that all the joints were square and the tenons fit snug into the mortises.  In the final assembly, however, one wants to make sure that everything is dead square; by which I mean that all angles are at 90° and all lines have 0° of variance.  I enlisted the help of my friend Alasdair Mac Roibeirt and his many bar clamps; together we trued all of the angles and clamped the coffer into shape.  We also bored the keyhole.

 

Tools and Techniques

Throughout the project, from the time I decided to make this coffer for Aelisia through the final step, I endeavored to use tools and techniques which were as close as I could to those utilized in the late Middle Ages.  To determine what those tools and techniques were, I studied extant examples of coffers with an eye for their methods of construction.  I looked for indications of tool marks (the distinctive marks left behind by tools, which can be used to identify the tool used).  I researched extant woodworking tools.  I reviewed inventories and probate records of deceased cabinetmakers.  Perhaps most helpful was a library of images I collected of tools, woodshops, and tools-in-use from paintings, drawings, illuminations, and engravings.

What follows is an inventory of the tools I used with accompanying evidence of their usage in the late Middle Ages with a focus on England and France.

Johann Comenius' The Cabinetmaker
Image of The Cabinetmaker from Jan Amos Komenský’s Orbis Pictus’, 1658

Beginning at a high level, I propose that the woodshop itself should be included in this inventory.  The woodshop is a dedicated space for woodworking, with the necessary light and space for the cabinetmaker to work, shelter from the elements for the raw materials, and storage for the craftsperson’s tools to keep them on hand and safe from damage.

 

Martin Loffelholz's workbench
Workbench showing end- and side-vises, dog holes, and an iron dog.  From the Loffelholz Codex, 1505

Next I list the workbench, which is more than merely a table.  The workbench provides a solid and stable, flat surface on which to work.  Additionally, a workbench incorporates means to secure the work to the table, such as vises and “iron dogs”.

 

 

Detail from Standebuch, Jost Amman, 1568
Detail from the Standebuch of Jost Amman, 1568

Saws are among the most recognizable of woodworking tools.  Frame saws (pictured) made efficient use of expensive iron or steel and were used at every stage of cabinetry: from turning timber into planks to cutting delicate curves.  Carcass saws (the quintessential handsaw) for both crosscutting and for ripping could cut planks and panels to exacting dimensions.  Back saws (short saws with a reinforced spine) were used for fine joinery.

 

 

Bit-and-Brace from the Mary Rose
A brace (with illustrated bit) from the Mary Rose

    A drill to bore holes.  Drills can be in the form of a twist -or bow- drill, an auger (a T-shaped handle with a fixed bit), or a bit-and-brace (pictured).

 

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Moulding planes, smoothing planes, and bench planes from Skokloster Castle, 1663-1664. Photo credit: Andrew Young.

Planes shear the surface of a board.  They can be set to do so with finesse, reducing high spots and irregularities, or aggressively, to reduce the overall thickness of a board with relative rapidity.  Additionally, planes may have shaped irons and soles to produce grooves and ridges for artistic effect or integral function.

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Mallet from the Mary Rose

 

2 thoughts on “A Coffer of Oak and Gratitude

  1. This is really neat! I am an art historian doing research on medieval woodworking techniques, and have been trying to track down any info I can find on medieval dowel plates – could you email me if you can help? Many thanks in advance!

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    1. Hi Lynley,
      Thank you! I believe yours is the first Comment left on my blog. I’m not at home for a few days, so I don’t have access to my full files. I can point you in a few good directions, however. First I recommend Polydore Vergil’s De Inventoribus Rerum. The later editions (1537 onwards, I believe) illustrate a dowel plate in Book III. I believe Albrecht Durer also had at least one dowel plate in one of his engravings, I think it was in Melancholia. Also I would recommend looking in inventories of cabinetmakers and related trades. Off the top of my head, I know that there is mention made in the Plea and Memoranda Rolls of the City of London in the debtor’s inventory of a wheelwright named Richard Crips (look for ‘dowelege bord’ or ‘doolpynne bord’; I forget exactly how it is phrased).
      Like many other useful (but shop-made and inconsequential) tools, dowel plates are not illustrated in art nor mentioned often in inventories. Quite literally they are just holes drilled in scrap metal or (rarely) wood. To anyone other than another woodworker I’m certain they just looked like junk.
      In a similar vein, I am currently trying to find early documentation of card scrapers (stiff metal sheets used to scrape wood smooth). It is very likely that the first card scrapers were just the backs of saw blades, or fragments of broken saw blade. Again, they were tools made of small, unremarkable bits of junk lying around the shop. They were neither of monetary value nor visual appeal, so documentation of them is proving quite difficult. When they first become mentioned (not until the mid-nineteenth century) they are referred to in terms which suggest that everyone knows of them and has for generations immemorial.
      I hope this helps. When I get back to my files I will try to remember to post more information for you.
      –Dunstan

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