Fake stone picture frame from XPS foam for a puzzle

In this article, we build a fake stone picture frame for a Marvel puzzle.

My kids and I really enjoyed finishing this marvel puzzle and were looking for a way to hang it on the wall.

CNC work in XPS foam

From a recent renovation project we had some leftover XPS foam. We used the CNC to make a special frame but the material is also easy to shape with a handheld router or a Dremel.
The CNC program is created in FreeCAD and rather simple. After a facing operation the CNC removes a bit more material from the area where the puzzle will be mounted so that it sits flush with the frame. Next we cut a groove all around the perimeter and cut the form free leaving tabs that hold the foam in place.


The surface finish of the CNC is a bit rough so I sand all visible parts of the foam smooth.

With a ball of tinfoil I give the frame a bit of structure by rolling it over the frame.

Painting a fake texture to create a stone picture frame

To protect the soft XPS and cover the green color I mix PVA glue with black acrylic paint.

This mixture is then applied to the frame and creates a hard surface.

With a piece of a kitchen sponge I apply some white, brown and mud-like color.

After these colors have dried I cover most of the color with a light grey. By applying the grey with a sponge not all the areas are covered and you get a pattern that looks similar to stone with inclusions.

Mounting the puzzle

While the grey color is drying let’s take care of the puzzle by first sliding a sheet of parchment paper under the puzzle to protect the table.

I apply a few coats of PVA glue thinned down with water so that it’s easier to spread it with a roller. The glue dries hard and transparent. It also creates enough of a bond to move the puzzle as one piece.

Next I apply glue on the foam surface and then carefully move the puzzle onto the backside.  Let the glue dry.

After the glue is dry the frame gets one more protective coat of watered down PVA glue. The the framed puzzle is ready to be hung on the wall.

Mounting a lightweight stone picture frame 😉

Hanging the puzzle is my favorite part. Just hammer two nails into the wall and clip off their heads.


The foam is so light that the nails can easily hold the weight. Just press the foam into the nails and it will stay in place.


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