Alaska Science Camps, Fairs & Experiments

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Spruce Gum

Modern technology has brought us many different sealants and adhesives.

Oldtimers had a traditional solution that was free, versatile and available almost everywhere: spruce gum. Oldtimers used spruce gum to fix leaky canoes and other watertight containers.

Preparing

If we try to apply spruce gum as it comes from the tree, it will not adhere well, and will soon crack. The secret is to heat a mixture of spruce gum with the right amount of oil or grease.

• If there isn't enough oil, the mixture will be too brittle.
• If there is too much oil, the mixture will be too soft.

Find out the right gum/oil mixture.

• Collect some spruce gum in a small can. Most older trees have an injury or two that is dripping gum. Many trees on top of cutbanks have such injuries from collisions by ice during breakup.
• Sew two pieces of birchbark together.
• Slowly heat the spruce gum in a small can, and carefully apply it to the seam of the sewn bark. When it cools, test it by bending and twisting.
• Now try the above with different amounts of oil mixed with the spruce gum.

What proportion seems to work best?

Experiment with different types of oil: vegetable oil, shortening, even motor oil. Use animal fats, like seal oil or bear fat if you can get some. What type of oil works best, or are they all about the same?

Different Temperature

You just conducted the experiment with the materials at room temperature. If you were patching a canoe, the gum mixture would be working at the temperature of the water in the lake or river. Put some on your fingers and test it in the water (don't burn yourself.) What differences do you see in the spruce gum mixture at this temperature?

I have used spruce gum to fix a boat in the past. Test the gum between your fingers in the river water, making sure the mixture was pliable at that temperature before applying it to the boat.

What is the ratio of gum to oil? What is the temperature of the water?

Is gum a better adhesive or sealant?

Now, prepare the best mixture from your experiment above. Put beaver, moose or other fur in the gum mix. Does this increase its strength?

What conclusions might you draw about spruce gum as a calk or sealant on a boat? Is there a difference in the types of spruce gum? Is the clear gum better than the gum that has turned white and hard, or do they both melt down well in the can?

You might also want to test the gum mixture as a sealant on different materials: birch bark, wood (dry and damp), aluminum, and skin (as used for skin boats). What conclusions can you draw from this?

Compare spruce gum with silicone or other sealants.

Is spruce gum affected by gasoline or other solvents after it is applied to a seam?

What conclusions can you draw about spruce gum as a sealant on the above materials? 

Other Applications

Spruce gum is also very effective to stop bleeding and infections in cuts. Oldtimers put spruce gum in a cut and left it there. Its medicinal value is high. Try softened gum in a cut the next time a small accident happens.

People who understand medicinal plants say to get gum from a young strong tree. A tree that is too small is like and infant, and isn't healthy enough yet. A tree that is too old is losing its life force. A tree that is the equivalent of a 20-30 year old person has the most resistance to bacteria.

Spruce gum is a healthy replacement for chewing gum. However, it is quite sticky. We sometimes heat it and mix in a little sugar, letting it cool again. Some gum is very dry on the tree, other gum is quite pitchy. Experiment to find the best gum for chewing. Don't be discouraged in the process. There is a certain texture you are looking for.

We chew spruce gum after eating salmon eggs to remove the sticky eggs and other food particles. Try it.

To remove spruce gum from hands or clothing, rub in some shortening. When it has removed the gum, wash them both off with soap and water.

	© 2004 Alaska Native Knowledge Network. All rights reserved. A partner with the Alaska Rural Systemic Initiative This material is based upon work supported by the National Science Foundation under Grant No. 0086194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
	Contents Camps as an Environment for Science & Culture Culturally Relevant Science Fairs Experiments		Also available in downloadable PDF