Patterns can be transferred to boards for cutting in a variety of ways.  Some people simply use tracing paper to transfer a pattern piece directly onto wood.  Spray on adhesives (available in hobby centers) are popular, but can leave residue (may need mineral spirits to remove).  My personal preference is to use rubber cement because removes easily without leaving much residue. 

Scroll Saw Blades

I find that a number 5 blade is good all purpose blade for most Intarsia work.  Number 3 blades are good for cutting very small pieces and re-cutting to eliminate gaps and number 7-12 blades are okay for ¾” or thicker wood and for hardwoods, but they leave wider kerf.

Good lighting is essential for accurate cutting so investing in a magnifying light highly recommended.  Keep wrists in a comfortable position to avoid carple tunnel syndrome (especially if you tend to work for hours at a time).  Attaching a tray onto your saw for blades and blade holders is also handy.  Ensure the blade is exactly 90 degrees to the table for most accurate results.

Some people use scissors or Exacto knife to cut pattern into individual pieces and then glue similar colored pieces onto a board for sawing.  This approach usually requires you to start with multiple copies of the pattern, but it allows the most efficient use of wood.

My preference, however, is to use a single pattern. I cut one piece, then move remaining pattern and cut the next piece. This may be a bit more time consuming, but to me it is worth it because I believe it provides the most accurate and best fitting results.  I also like to keep another copy of the pattern available to place the pieces on after I cut them rather than numbering the pieces as some people like to do.

3D Effect

To make an Intarsia project stand out, use shims to slightly raise pieces that should appear closer to the viewer. Keep a supply of scrap wood on hand in thickness ranging from 1/16” to 1/4”.

Sanding

The most critical and time consuming component of Intarsia process is the sanding. Each individual piece should be sanded at least 3 times.  Pneumatic drum sanders are very popular for intarsia, but use of small sanding drums on a Dremel tool is also handy.  Start with rough sanding the “lowest” pieces with a medium (80) grit sandpaper. The goal here is to get an initial impression of how the project will look. Use a pencil to mark the finished level of any adjacent pieces that have already been sanded and then sand down to the line so the pieces “match“.  After all pieces have been rough sanded, change to a finer grit (120-150) and sand again.  Placing a slight bevel around the edge of each piece produces a shadow that helps hide inadvertent gaps.  When all pieces have been sanded at least twice, and the project looks good to you, re-sand each piece again by hand with 180-220 grit sandpaper.

True Intarsia projects do not utilize stains, but rather the careful selection of wood species and grains.  There are no "rules", however, so if you think a stain makes it look better - go ahead! 

Clear polyurethane gel is easy to use. Apply with a lint free cloth or paper towel, let dry a few minutes, then wipe off excess. Applying 1-3 coats individually to each piece can be time consuming, especially when you get into projects with more than 100 pieces .

An alternative is to assemble the project first, and then apply 1-3 coats of a wipe-on clear liquid polyurethane.

Use another copy of the pattern to cut a backer board from ¼” thick Masonite or plywood.  Cut about ¼” inside the outer boundary so that it will not show around the edges.  Dry fit pieces onto the backer board before glueing pieces onto backer board using white or yellow wood glue.  After glue has dried, apply a picture or wire hanger to the back (depending on size and weight)