Kintsugi

[fredtruck]

Kintsugi is the Japanese art of gold joinery; that is, broken pottery is repaired by joining the pieces back together with resin and gold dust.


A few weeks ago, a straight-line wind clocked at over 100mph went through my back yard, destroying the few bonsai I had left outside. One of the victims was a square bonsai pot I am particularly fond of. It was cracked in diagonally opposed corners.


I inspected the damage.



This corner was the damaged the worst.




The crack ran deep down the side of the pot. As I worked on the pot, another crack became apparent, very close to the first and more visible one. I used an epoxy putty called EP-400. It sets up in 15 minutes or so and is incredibly hard.

I used a couple of different methods of finishing the putty. I employed very coarse sanding sticks, but eventually, I found that my Dremel rotary tool with a sanding cylinder run at 5,000 rpm was the best.



The parallel crack corner, above and below:



Laying the putty down.



Here, the finishing of the putty is partially complete. Next, the putty is completely smooth. Notice how the cracks almost completely disappear:


The single-crack corner is even less visible:


The Gold Leaf paint, applied:



In looking at Japanese examples of Kintsugi, I noticed there was an abstract expressionist feel to the way they laid the paint down. I followed their example feeling this type of brush work expressed the trauma of the pot being damaged.



Here is the less damaged side:

 

[just.wing.it]

Awesome!

 

[MACH5]

Wonderful tutorial Fred and great job! This is very useful to me as I have a couple of pots I'd like to repair. Sometimes it adds to the character and beauty of a container. Thank you for sharing.

 

[M. Frary]

I put some back together with gorilla glue this spring.

 

[fredtruck]

I'm sure gorilla glue will work as long as it's not water soluble. If you're actually joining pieces together, I recommend the strongest epoxy you can obtain. In the instance above, epoxy putty works because the pot is just cracked, not completely broken.

 

[M. Frary]

I'm sure gorilla glue will work as long as it's not water soluble. If you're actually joining pieces together, I recommend the strongest epoxy you can obtain. In the instance above, epoxy putty works because the pot is just cracked, not completely broken.

It's what was on hand and they weren't expensive pots Fred.

 

[fredtruck]

Got it!

 

[Dorky_gearhead]

In traditional mindsets this pot is now more beautiful than before the damage occurred

 

[drew33998]

The only issue with epoxies and gorilla glue is i find that they swell up. Which can leave a larger crack

 

[Arcto]

I've played with different bonding glues, epoxies from time to time. One thing I've read repeatedly on labels is they are not recommended at below -10F. My experience with gorilla glue has not been good. No longer use it. I've never tried EP- 400. Fred, do you know what it's recommended minimum temp is?

 

[fredtruck]

Sorry it's taken so long to get back to you. No, I don't know what its recommended minimum temp is. I've also been unable to find out. It is used by jet fighter mfgrs. so I'm fairly certain it resists heat well.

 

[0soyoung]

do you know what it's recommended minimum temp is?

Are you trying to glue a pot back together when it is 10 below?

AFAIK, the recommended minimum is for the application/curing. Once cured it is simply a matter of the expansion coefficient relative to the material being bonded (it is difficult to imagine how this can be covered by a generic temperature spec).

 

[0soyoung]

The only issue with epoxies and gorilla glue is i find that they swell up. Which can leave a larger crack

One must clamp the pieces together, which is not always easy. I've succeeded doing so with with several pots (often using a plastic pot as the clamp) and it performs very well. It is easy to pare off the cured excess; joints are strong and durable). The glue line also paints easily.

But, if you can't clamp the pieces in position, I agree that Gorilla glue is a total nightmare (been there, done that too!).

 

[Mellow Mullet]

Great thread, Fred.

The plant where I am employed makes all kinds of polymers (epoxies) and hardeners, as a lab tech, I do a lot of gel testing. Oso is correct, cure rate, pot life, and gel time are all extremely temperature dependent. The -10 degrees is the lowest temp that the two components will cure. Clamping is also a must, there should be as little space between the two pieces as possible.

You can minimize the sticking of the excess by applying a release agent close to the crack, just be careful not to get on the joint. Or, after clamping, with the excess off with isopropanol or acetone before the epoxy cures.

John

 

[Adair M]

I’ve done a couple of these recently, and found that aregular old two part epoxy mixed with some gold does the trick

Here’s one I did:

 

[fredtruck]

Do you then smooth the bead that resulted?

 

[ysrgrathe]

I'm sure gorilla glue will work as long as it's not water soluble. If you're actually joining pieces together, I recommend the strongest epoxy you can obtain. In the instance above, epoxy putty works because the pot is just cracked, not completely broken.

Gorilla glue is polyurethane. It is not soluble in water, although it isn't really designed for underwater application either. It will likely last a good long time in this application. I experimented with gluing deadwood to stone with it, still holding up years later.

 

[Tieball]

If applicable....How do the epoxy only and the epoxy gold joints hold up in winter?

I have one pot that has a crack....I plan epoxy for the fix. But have not done it yet. I’ve been thinking that the repair is fine for the non-winter months but I’d need to slip the tree out of the pot for the winter to prevent expansion re-cracking. I’d just plant the tree in my sandy soil for the winter and in spring return it to the pot.

 

[Potawatomi13]

Could make/use metal strap screw clamps like on radiator hose for curing or Winter. Some months past asked Ryan Neil on a visit about pot repair and as understood actual gold was used as the cement. As he was busy did not ask for more detail.

 

[Mellow Mullet]

Do you then smooth the bead that resulted?

I assume you are asking about @Adair M 's repair. It looks to me like the small bead he has is a result of application, it is what oozed out of the joint when he pressed it together. It looks nice. The trick with epoxy is to use as little as possible, more is not necessarily better. I have not repaired a bonsai pot, but I have repaired a vase and I have a lot of colleagues that bring stuff to lab to see if we can "fix" them together. The trick is to carefully apply a small bead to one side, then carefully press and clamp, if possible, the two pieces together. What is pushed out of the gap when the pieces are clamped forms that nice bead, and it will be smooth and shiney when it cures, just don't touch it until it has fully cured, the oils and moisture in your fingers will dull the finish on uncured epoxy.