The production process of Tongmu coffin

The production process of paulownia coffins is based on traditional woodworking techniques and combined with burial needs to form a relatively fixed process that emphasizes both structural stability and respect for the deceased. The key steps from material selection to finished product are introduced as follows:

1、 Material selection: Choose suitable paulownia wood

1. Wood selection

Priority should be given to selecting paulownia trees with a longer growth period (usually more than 10 years), with a trunk diameter of at least 30 centimeters, ensuring that the wood texture is straight, without obvious scars, cracks, or insect marks.  

Choose the main trunk of paulownia wood as it is not suitable for making the main board of coffins due to its fine branches and uneven texture.  

It is necessary to avoid using newly cut "raw wood" (with high moisture content), and it should be naturally dried or dried (usually for more than 6 months) to reduce the moisture content of the wood to 15%~20%, in order to prevent deformation and cracking of the coffin body due to shrinkage after production.

2. Sheet metal processing

Cut the dried paulownia wood into the required boards for the coffin body, including the coffin lid, coffin body (two side support plates), coffin bottom (bottom plate), front and rear baffles, etc. The thickness of the boards depends on the specifications of the coffin (usually the thickness of the coffin support is 5-8 centimeters, and the bottom plate is slightly thinner, about 3-5 centimeters).  

Use a planer to level the surface of the board, ensuring that the contact surfaces of each component are smooth, laying the foundation for subsequent splicing.

2、 Cutting and Forming: Processing Components According to Specifications

1. Determine the specifications of the coffin body

The size of the coffin body needs to be determined according to the deceased's body shape or local customs. The common traditional specifications are "seven feet three in length and two feet four in width" (about 2.4 meters x 0.8 meters, slightly different in different regions), with the coffin lid slightly larger than the coffin body, forming a interlocking structure.  

The front and rear baffles are mostly trapezoidal or curved (narrow at the top and wide at the bottom), and the mortise and tenon joints need to be planned in advance at the junction with the side panels.

2. Fine machining of components

Mark the dimensions and mortise and tenon positions on the board using tools such as ink pens and angle rulers. "Mortise heads" need to be machined on both ends of the coffin body's side panels, and "mortise holes" need to be machined on the corresponding positions of the front and rear baffles. In some areas, "tongue and groove joints" (the edges of the board are processed into a concave convex structure and interlocked) will also be used to enhance sealing.  

If the front and rear baffles are curved, tools such as adzes and chisels are needed to chisel the wood into an arc shape. Some exquisite techniques will carve simple patterns on the baffles (such as auspicious clouds, lotus flowers, etc., symbolizing good luck).

3、 Splicing and assembly: focus on structural stability

1. Jointing with mortise and tenon joints

The core connection method of the coffin body is a mortise and tenon structure (without nails, to avoid metal corrosion affecting the stability of the coffin body, and also in line with the traditional concept of "burying in the soil for safety"). Align the tenons of the support plate with the mortises of the baffle plate, lightly tap and embed to ensure a tight joint without looseness.  

The connection between the bottom of the coffin and the upper board is also made using mortise and tenon or tongue and groove joints. In some areas, a small amount of tung oil ash (a mixture of tung oil and lime) will be applied to the joint to enhance waterproofing.

2. Coffin lid production

Coffin lids are mostly made of integral boards or assembled from 2-3 boards, connected by mortise and tenon joints. After surface planing, the edges can be processed into slopes or arcs to ensure a tight fit when fastened to the coffin body.  

In some areas, a "sky beam" (a horizontal wooden strip to enhance the load-bearing capacity of the coffin lid) will be added to the top of the coffin lid, or simple lines and patterns will be carved as decoration.

4、 Polishing and Finishing: Enhancing Surface Texture

1. Fine polishing

After assembly, use coarse sandpaper (80-120 mesh) to polish the surface of the coffin body, remove burrs and joint marks, and then use fine sandpaper (240 mesh or more) to polish the surface smooth and flat, avoiding wood burrs from hooking the deceased's clothes.

2. Painting and anti-corrosion

In traditional craftsmanship, 2-3 coats of tung oil (or varnish) are applied to the surface of the coffin, which can prevent moisture and corrosion, as well as make the wood texture clearer. In some regions, according to customs, the outer wall of the coffin will be painted black, red, or wood color (black symbolizes solemnity, while red in some regions means "joy and sorrow").  

If anti-corrosion properties need to be enhanced, a layer of tung oil ash will be applied to the surface of the wood before painting to fill small gaps, isolate moisture and insects.

5、 Characteristics of traditional craftsmanship

Nailless: The core relies on the mortise and tenon structure, reflecting the wisdom of traditional woodworking of "connecting wood with wood" and avoiding the influence of metal corrosion on the coffin body underground.  

Practicality first: Compared to furniture, paulownia coffins have less decoration and place more emphasis on structural stability and sealing to ensure the protection of the deceased during burial.  

Regional differences: The craftsmanship details vary slightly in different regions. For example, humid areas in the south place more emphasis on painting and anti-corrosion treatment, while dry areas in the north place more emphasis on wood drying and structural crack prevention.

Although the production process of paulownia coffins is not complicated, each step revolves around the core requirements of "stability, anti-corrosion, and solemnity", which not only reflects the utilization of wood characteristics, but also carries the care and respect for the deceased in traditional funeral culture.