Chimney Build

I have had a request to describe the technique used in constructing the chimneys on my models.  The following photos show the process I use to create the patterns and ultimately the castings.

After determining the size of the chimney build up the core from styrene.  The top is then built up from various widths of .020 thick styrene strips.  The final individual brick layer is .030 x .020 strip stock.  The two cores seen in this photo have a different number of courses on the caps.

This is an end on view of the cores and cap.  As can be seen this chimney is rectangular in cross section.  When the final chimney is assembled the seam will be on the corners not down the side.

Here we have a arch top chimney core.  In this case I started with a solid styrene strip and rounded over the top.  Once I had the desired shape I sanded down the back diagonally across the strip to form a core similar to those shown in the prior photo. 

Next make molds of the cores.  Note that the mold on the left was take of the cores before I added the trim strip as seen on the center mold.  There is no point in having to recreate a completely new core when I could capture the desired core in the construction process.

Next I pour hydrocal castings of the cores.  I sand the backs flat and clean off any flash.  On the left is the chimney with the trim strip, on the right without.

Use a soft pencil to sketch the brick pattern on the core.  I use a 3" mortar spacing.  Once the sketch is done I use a sharp scribe and scratch out the lines.  This is a slow process but you only have to complete one good pattern.  If you make a mistake do not hesitate to start over, the pattern in this photo is one that I rejected.

I then epoxy the completed patterns to styrene.  I fill any edge gaps with green putty, build up box walls and pour the rubber molds.

These are the molds ready for hydrocal.

Here we have the completed casting pairs (only one side shown for round top chimney).  Carefully sand the backs flat and then glue the halves together to form a complete chimney.