How to Cook Colored Varnish
Resin
This is meant to be a simple picture essay to describe how I cook the colored resin that I use in my
violin varnish. I have tried my best to photograph every step of the process so that other violin
makers can try themselves. One thing that I have not shown in the pictures is the fire extinguisher
that is always kept close to where I bbq/cook varnish. Cooking varnish involves heating potentially
flammable ingredients over a fire. Accidents can happen, whether cooking varnish or bbq-ing
chicken,  so you must be prepared.
Find a metal container to
cook your varnish resin in.
You could go to the store
and buy a cooking pot for
this but I prefer to save a
few old aluminum cans and
just cut the lids off with a
standard can opener. I just
use each can once then
dispose of them.
Find a place OUTSIDE to
cook your varnish. Do not
cook violin varnish inside
your house. Cooking resins
releases a lot of smoke and
who knows what else that you
should not be breathing so do
not cook this stuff inside your
house, shop, or a building
unless you are a chemist with
a proper fume hood, etc.

I cook using a small charcoal
bbq that I bought new last
year for $3.
Place your cooking
containers in the bbq to
determine how much
charcoal to use. You just
want a ring of charcoal
around the base of the
containers.
Remove the cooking
containers and then light up
the charcoal. While the coals
are heating up it's time to
mix up the varnish
ingredients, there are just
two of them.
The two ingredients are plain
white sugar and tree resin.
The tree resin that I have
always used in the past is
rosin which is a processed
form of pine resin. A bag of
rosin chunks is seen on the
far right hand side of this
picture. Now that I live in an
area with forests I have
started driving into the
mountains every now and
then to collect my own resins.
One the far left is a jar filled
with pine resin that I have
collected from local pine
trees and beside it in the
smaller jar is spruce resin. I
have found that the spruce
resin makes a more brown
colored varnish than plain
rosin. Tonight I will be
cooking both pine resin and
rosin varnishes to compare
the colors produced.
Into each beer can I have put
two tablespoons of sugar and
two tablespoons of resin. The
can on top happens to
contain the pine resin that I
have harvested and the
bottom can store bought  
rosin.

I would not put any more
than this amount of
ingredient into the cans. The
mixture is going to boil and
bubble strongly when heated
and you do not want it to
overflow. The amount of
resin in each of these cans
will be more than enough to
color the varnish of a violin.
Once the ingredients are
combined it's time to set the
cans on the bbq. Line up hot
coals around their bases as
shown here. After about 10-15
minutes all of the ingredients
will have melted. I would
resist the temptation to stir
the mixture. Soon it will
begin to boil. Once the boiling
starts the varnish will be
mixing itself so there is really
no point to stirring it. Also by
stirring it you risk burning
yourself or spilling the resin.

Just let it sit and do its thing.
It'll be fine.
Notice how the resin in the
green can has boiled up and
is near the top of the can. If I
had used more ingredients
then it would have
overflowed.

The sugar in this recipe does
not actually mix into the
resin. What happens is that
after the sugar turns to
caramel but right before it
turns to carbon it somehow
reacts with the resin and
gives its color to the resin.
When cooked properly there
will not be any sugar left in
the resin.

When is this resin fully
cooked? When all of the
sugar has turned to carbon.
You can see this visually or
by poking a stick in to feel for
large lumps of carbon. This
will take more than an hour
but less than two hours. Too
much or too little cooking
results in less color in the
resin or little colored resin.
Once the resin is through
cooking and has cooled down
to room temperature it is
time to separate the resin
from the carbon. This is done
simply by dissolving the resin
in denatured alcohol. Let the
solution sit long enough so
that the resin is dissolved
and the carbon settles out.
Then carefully pour the
liquid into a jar, you can
filter it through a coffee filter
if you want but I don't.
This is the resulting solution.
There were still some
particles in this batch but
they will settle to the bottom
of the jar if it is left
undisturbed long enough.
They are visible in this
picture because I had just
shaken the jar.

This resin is most easily used
for tinting spirit varnishes.
When I varnish violins in the
wintertime I typically just
use a combination of shellac
flakes and this colored resin
for my varnish.

It can be used in combination
with oil varnishes, and this
gives the best appearance,
but doing so is tricky. If done
improperly linseed will
bleach out the color of the
resin as it dries. If done
properly the color is stable.

At the right is a violin which I
have just varnished using the
spruce resin which I cooked.
The color seen is due to the
resin, I did not use any
shellac on this violin.