Restoring a Glue Pot

20151026_171723Traditional hide glue was prepared in Glue Pots.  Hide glue is used in making violins for a variety of reasons, don’t take your violin to anyone who doesn’t use traditional glues they could seriously damage your instrument.  Read more about hide glue here.

Before the 20th century and the advent of PV glue, glue pots used to be as common as frying pans.  I found this typical old glue pot and decided to fix it up.  At one point it may have been enameled, this prevented rust from coloring the glue.  I won’t use the glue pot for my own work, but I like to have a 100+ year old glue pot on the shelf to put things in perspective.

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The pot is cast iron, I removed the rust by soaking in vinegar (this will etch the surface and would cause visible damage if the surface were polished, but this pot won’t notice).  I then ‘seasoned’ it with olive oil like you would a cast iron pan.  You can see the final result at the top of the post.  It turned out quite nice I think.

09a0282v1Lee Valley now sells a small stainless steel pot replica which would work well if you like the traditional look and feel.  It can be used with a small electric hot plate or coffee cup warmer which they also sell.


Maybe the greatest promotion of Classical Music in the Internet Age

Today, December 17th, Google updated their ‘doodle’ to celebrate classical music.    The doodle is the GoogleDoodle
‘Google’ graphic at the top of the google search engine.  In the past this has been variations on the google wordmark to celebrate various anniversaries.   This one is special for two reasons, it celebrates the 245th baptism of Ludwig van Beethoven (his birthdate is unknown) and it is also Google’s first interactive doodle.

Why is this big?  Google is the most used search engine in the US, and process about 40,000 searches per second, about 3.5 Billion per day.  Doodles are often country specific, but this one is worldwide.

The interactive google tells the story of Beethoven out on the town with his freshly written score.  A series of mishaps cause the score to get mixed up, and the viewer is played a melody and then has to correct the arrangement of segments of the music.  Getting it right moves you along in the story.

This is great exposure for classical music that will reach a broad audience.  Bravo Google!

Play the interactive Google Doodle here.

Distractions: A Workshop Hydgrometer

Some plate tuning methods call for accurate measurements of wood moisture content.  One way to determine the moisture content of wood in your workshop is through lookup tables of relative air humidity levels and temperature, like this one.  Note however that wood takes  a while to adjust to relative humidity changes in the air.

Digital hygrometers are readily available, generally with accuracies of +/- 2%.  These read humidity almost instantaneously.  But you can create a serviceable relative humidity meter can be made from wood.  Wood expands and shrinks with variations in relative humidity, and expands at different rates in different grain directions.  By using the different relative shrinkage and expansion rates, you can make a hygrometer from wood in the same way a bimetallic strip measures temperature.

For example see this picture from my friend Mathias who did measurements on various wood species and grain directions in his workshop in Ottawa.  The picture on right demonstrates that wood shrinks most tangentially.  Axially (in the up-down direction as the tree grows) the variation in shrinkage and expansion is smallest.  By combining these we can make a hygrometer.

CaptureThe hygrometer is made by selecting two hardwood strips, one cut axially-along the grain, and one cut tangentially or across the trunk of the tree, also known as slab cut).  The diagram on the left illustrates this.  These two pieces, or segments of pieces if long pieces aren’t available, are glued together.  The relative humidity when the pieces are glued will determine the point where the hygrometer will be straight.  Likewise, a water based glue can be used, but this will increase the moisture in the wood and cause the midpoint to be offset.  To avoid this epoxy can be used.

55%21%The sensitivity of the hygrometer will be determined by the thickness of the pieces glued together and the length hygrometer.   In my experience a long hygrometer (75cm) of about 3.3mm total thickness moves about 8.5mm per % change in relative humidity.  The hygrometer needs to absorb moisture so it’s ill advised to put a protective coating over the hygrometer.  Analyne dyes are a  good alternative to color the hygrometer.calibration