More on the Paper Sandwich
16.06.23
I've been trying your 'paper sandwich' method for holding work, but some parts of my carving didn't stay glued down. What am I doing wrong?
The so-called paper sandwich' is a particularly good way of holding a flat carving that is either too small, too delicate or just too awkward to hold in any other way.
Simply put, you glue cartridge or watercolour paper between a backing board and, say, your relief panel. The carving is held securely as you work and when you're finished you split the paper and release the carving.
If you don't know of this method of holding work, check out the video link at the bottom of this blog.
What might be the causes of the this method failing, prematurely releasing all or part of the carving?
Pass me a sandwich. Time to put my thinking hat on:
Glue
1. The glue is too dilute - Full strength wood glue is pretty heavy duty for this operation but if you dilute it toom much it'll loselose grip. Diluting with something like 30% water is enough.
2. Not allowing everything to dry - This is a common reason for paper 'give'. Don't be impatient! Allow the sandwich to fully dry in a dry, warm room overnight.
3. Too lightly clamped - Make sure you clamp all over the workpiece and board. You want to see squeeze-out around the edges. (But don't clamp too hard; over-crushed paper is difficult to release.)
Backing board
1. Flat - Use a good, flat piece of wood. Ply or MDF is best; something that resists warping.
2. Not too thin - Your backing wood must be thick enough to remain stable and resist the pressures that your carving wood might exert as you remove material from it.
3. Smooth - It's a joint, yes? A flat-to-flat face with paper (backing wood and carving) in between is what you want. Not smooth enough and there won't be enough grip.
Consequences:
Because of the above factors, the paper may gives way, usually at a corner or edge of your carving, which bounces up and down with fresh air beneath.
It may also be the carving warping as the free surface loses water to the air and shrinks, or with a change of internal pressure in the wood as you carve. Thus the carving pulls away from the inadequate paper sandwich filling and you have a lifted corner or edge.
Here's the problem:
One of the joys of the paper sandwich is the back edge of the carving is supported, so you can carve through into the backing board without splitting away the back edge of the carving. You then split the paper and, voila you have a pretty clean edge.
Now, with a free edge, you can break away wood from the unsupported back of your carving, even break bits off.
What to do - some options:
1 Brush some fresh glue into the gap - diluted as before, and re-clamp.Be careful: if warping has happened, forcing the wood down to the back may split it.
2. Remove the whole piece - then flatten the back on glued-down sandpaper and re-sandwich
3 Support with a wedge - If you have finished that part of the carving you can simply support the edge and move on.
Related Videos:
Examples of the Paper Sandwich in action: