Different techniques of Kintsugi
Breakages are unfortunately par for the course in our business and so we have a ready supply of items suitable for Kintsugi.
Kintsugi (金継ぎ, meaning "golden joinery"), also known as kintsukuroi (金繕い, meaning "golden repair") is a traditional Japanese technique for mending ceramics. In another post we go into the history and philosophy of kintsugi, but in this post we will talk about the technical side of kintsugi. There are many different ways of doing kintsugi. In essence, there are two basic parts to the technique: how to glue the piece together and then how to hide the mend with gold.
The different glues to use in Kintsugi:
There are four materials that are generally used as a glue, and in order of difficulty to apply they are: Urushi lacquer, cashew paint resin, synthetic resin, and epoxy glue.
- Epoxies are widely available at DIY stores or craft shops and they are easily worked and can be wiped away if you make a mistake. However, they often aren’t tested for use with food and shouldn't be used on items you will eat or drink from.
- Synthetic resins are slightly less widely available and are not very heat resistant, and they can be tricky to use with earthenware (but are very good for gluing china and glass). They also are not usually food safe, so the same as epoxies, they shouldn't be used on items you will eat from.
- Cashew resin works as a glue, but it is more commonly used for furniture and has a strong smell, so it isn’t the best thing to use for high quality items that may be used for food and drink.
- Urushi lacquer is the hardest to use for a couple of reasons: it is poisonous in its natural state and is highly allergenic; refined urushi hardens on contact with air in a humid environment, so humidity has to be controlled; and, it is harder to wipe away and start again. But the positive about using urushi lacquer compared to the others is that it is a natural substance that is totally food safe and has been used over thousands of years for traditional Japanese tableware.
Many Oriental cultures initially used urushi as an adhesive (along with other wood saps and naturally occurring substances like bitumen) both to mend pottery but also to fix arrowheads for example. Subsequently, they discovered that once urushi sap hardens, it is resistant to heat and alcohol, it is waterproof and is also resistant to acidic foods and liquids. Then came the hard work of refining and applying coats of multiple coats of urushi to objects. We know that urushi was being refined and used in Japan in the early Jomon era (10,500 to 300BC) both for practical and decorative purposes, and as Conrad Totman puts it in Japan: An Environmental History:
“Perhaps the most interesting aspect of these artifacts – and an aspect that helped them survive to the present – is that Jomon craftsmen coated many of their products in lacquer. Throughout the Jomon era, lacquer was used despite the trickiness of its production.”
Lacquered kettle-shaped pottery from the latter half of Late Jomon period, Kakinoshima site (Photo: Cultural Properties Division, Lifelong Learning Department, Hakodate Municipal Board of Education). Lacquer seems to have been used for many decorative purposes as well as practical purposes in the Jomon, with red being the favoured colour.
Tanaka san uses urushi lacquer both because it is the safest and because it is the traditional way. Epoxies and modern kintsugi kits are great ways of having fun mending your ceramics, but we love using a material which has been used for thousands of years back to the Jomon era.
The different types of gold decoration in Kintsugi:
The big distinction here is between using a gold-coloured liquid and using actual precious metals. Kintsugi can use silver, 22k or 24k gold – each will bring its own character to a piece. We tend to choose 22k gold, the extra shine on 24k often jars against a glaze, whereas the soft lustre of 22k gold is a beautiful contrast against a vitrified glaze. The gold is delicately applied as a powder and our taste is to use a minimum of gold so that a mend looks like delicate tracery across the piece rather than a thick vein of gold.
“Liquid gold” or gold paint is included in many DIY kintsugi kits and is much easier to apply than gold powder. It can easily be brushed on with a paint brush and can also be wiped away if you make a mistake. It is also cheaper than using real gold! Kintsugi kits fulfil a purpose and can be a great way to mend your broken items if you are good with crafts, but it shouldn’t be confused with traditional kintsugi, after all the Kin in Kintusgi means gold!
If you are looking for a good quality kit try something like this from Oxford Kintsugi. She clearly states the limitations of the kit and whether the ingredients are food safe or not. Using Brass powder is also good practice for using gold in the future.
Once gold is applied, it is very hard to spot the difference between the different glues, but on some earthenware and pieces with a more porous glaze, you can see a faint yellow halo around the mend which is where the lacquer has seeped into the glaze. Also, if the gold is very smooth, it is very likely to be a synthetic glue with some type of liquid gold. It is very hard to get a completely smooth, flawless surface on a genuine kintsugi mend. Some menders use a synthetic glue to start with because it is cheaper and easier to set, and then they will add a layer of lacquer as a topcoat. Tanaka san doesn’t approve of this, as long as there is a chance that his customers will use his pieces as tableware, he will carry on using natural urushi. He follows the traditions from 700 years ago, which can be inefficient in time and money, but his professionalism means that even where you cannot see, he will make sure the work, technique and materials are top quality.