I made some home-made casein glue using this online recipe. It was incredibly easy. I clamped two pieces of redwood – roughly 1’x2″x2″ – together with some of this concoction and let it cure overnight.

In the morning, I found two pieces of redwood that were very strongly glued together. I was unable to pull them apart with my hands. I threw them on the cement ten times with all my might – they remained intact. I threw them against the sharp corner of a concrete step ten times with all my might – not only were they intact, there was absolutely no sign of weakening.

I submerged them in water overnight. In the morning I found two pieces of redwood that could be pried apart with my hands with fairly little effort.

I’ve  read that casein glue is water resistant. It may be possible, considering the design of these surfboards where the glue has no immediate exposure to water, to use this glue. The potential issue would come from dings and tiny cracks that let water through to the glue. This may not be enough of an issue considering the high amount of surface area where there will be glue. Trial and error are the only ways to truly test this.

Another preoccupation is that the glue was very clumpy and, because of this, didn’t allow the two pieces of redwood to clamp together as closely as I’d like. This could possibly be fixed by using more water during the final mixing stage. If anyone has experience making casein glue, comment below, I’d appreciate your insight.

5 thoughts on “Casein (milk) Glue

  1. Hi Nate,
    Really interesting what you are working on. I am actually working on the same goal to invent a 100% biodegradable surfboard for the past 2 years.
    I am also working a lot with casein glues where I was able to get “waterproof” and high strength glue joints.

    I used casein powder (bought online) in mixture with lime putty.

    But I am really new and didn’t heard of shellac yet. Send me a mail if you are interested in exchanging some knowledge.

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    1. Hi Sebastian,
      Thanks for reaching out! That’s really cool that’s you’ve been working on the same thing. Id be interested to see what kinds of results you’ve had with casein glue. I had pretty good results with the stuff I made. It was able to stay under water for two days until it lost its bond. I’ve heard about adding lime to make it more water resistant. I also heard that it decreases the working time you have to get the pieces glued. What’s been your experience? My next goal is to make my glue much less chunky. I would imagine buying the powder would be a good way to go. I’ll try making my own using a coffee grinder.

      Shellac is very nearly the perfect coat to put on the outside. The only issue is that it fogs up really bad after being in contact with water. It looks hideous. However, despite its ugliness, it still holds up well in water, even after several days of being fully submerged. The reason it turns foggy is because water gets inside. For some reason it doesn’t ruin its structural integrity. If there was something that could be mixed in to make the shellac less porous it would definitely be my choice for the outer waterproof coat. You can buy shellac flakes online and mix it yourself and experiment. Let me know if you need a good source to buy these.

      Looking forward to tossing around ideas. Do you have anything online of what you’ve been doing?

      Cheers

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  2. Hi Nate,
    I actually had some samples with different ratios of lime, casein powder and water in the water for 14 days. Most of them where still intact and a had a strong bond. The thing is casein glue can still take up water after its hardend which decreases the strength but as soon as it’s dry again has nearly the same properties as before. Ah ok I didn’t know that lime decreases the pot life but I know that it depends a lot on how much water you put in or you can even make the surface of the wood wet before you glue it to get more time in working. Casein glue hardens when wood and air absorb the moisture. I can really recommend getting casein powder, I tried it with curd too but couldn’t get close to the results with powder.

    Shellac sounds really interesting! I did some research yesterday and heard that the first one or two months water has an effect on it but as you leave it longer it’s getting resistent against water spots and fog. Need too try that out when I am back home. I am currently in South Africa on exchange and I am from Austria. I am doing tests at my university for this project. Testing in saltwater and on weathering with mostly casein glue and different coatings.

    I don’t really publish much of my work but as soon as I know it’s working will start with that. You can find me on Instagram where I mostly show the process of building a wood surfboard. @basti_fre

    I also experimented with resin glues and got the best results with adding coal, bee wax and small fibers. The bee wax makes it more flexible and fibers add the strength.

    Cheers!

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    1. Some really great insights! Thank you so much for sharing. Do you think that adding the lime to the casein is mainly for water resistance or does it add strength as well? 14 days underwater is an amazing result!!Thats so cool. Did you get similar results without using any lime?

      My friend used shellac for his kitchen counters. It encounters water everyday from washing dishes and food preparation. He used 8 coats. It’s been on for a couple years. It’s very durable and doesn’t fog up anymore. I put my test pieces in water after a couple days and they completely dissolved. I put another one with 8 coats after a month and it is still very hard but very very foggy. However, after a few days, the fog goes away a little. For my project, I’m more concerned about the durability than how it looks. If it works even though it looks a little beat up, that’s okay. And, over time, like you mentioned, it won’t get as foggy.

      What kinds of resin did you experiment with? Pine?

      Cheers

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  3. Hi Nate,

    Yes the reaction between lime and casein makes it waterproof but it doesn’t add strength. i think it actually decreases the strength by making the hardened glue more brittle. Casein itself mixed with water is not waterproof, didn’t try that out though. When you mix casein with lime you can see smell and hear the reaction between them.

    I just went into the woods and got some resin from pine and fir. Afterwards I filtered it through a sock with boiling water.

    cheers
    Seb

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