Use Of Kintsugi Repaired Dishes For Food

Nowadays, kintsugi refers to two very different ways of repairing ceramic or, for example, glass objects. In terms of the use of repaired items for food and foodstuffs in general, it is really important that, on the one hand, the materials used for the repair are food safe, and on the other hand, that the repaired items are used correctly so that they do not break down again, requiring a new repair.

Summarized below is information how the method of kintsugi and materials used to repair the dishes impact the possibilities to use the dished for food. Also listed are the most common instructions for using, storing, washing or, for example, heating kintsugi repaired objects. In the following instructions and presentations below, we refer to traditional kintsugi and, excluding the technique demonstration part about modern kintsugi, all instructions are for traditional modern kintsugi repaired objects.

The method of the repairing affects objects food safety
All methods used to repair broken ceramics do not restore the object safety to be used for food. When it comes to kintsugi, there are nowadays traditional and modern kintsugi. Which method is used to repair the object has a decisive influence on whether, for example, the repaired dish is suitable to be used for food.

Traditional kintsugi means repairing broken ceramic objects using the traditional Japanese kintsugi method, basically using only 100 % natural materials. However, the fact that an object or dish has been repaired with traditional kintsugi does not make it food safe. Although kintsugi literally means joining with gold (Kin = gold and Tsuki = to join), due to the high price of gold, in traditional kintsugi other natural materials, that are not food safe, can be used alongside gold. This is often the case with objects that are not for food, such as decorative objects.

These parallel materials are used to replace the expensive gold dust that is attached to the seam of the finished object with urushi lacquer during the finishing phase, and the raw materials of the alternative metal dusts used are, for example, bronze, aluminum, mica (mica = ground silicate mineral) and other gold-colored materials, which are ground into fine dust like real gold. Along with gold, in traditional kintsugi, the more affordable silver is often also used. We still often talk about kintsugi, although the more traditional name would be gintsugi (Gin = silver and Tsugi = to join), i.e. joining with silver.

Dishes finished with silver powder are sometimes sold as food safe. However, this is based in the tradition and using silver to to fix dished for food is not allowed by existing food legislation regarding food contact materials. Although the occasional use of silver repaired dishes for food is most likely not dangerous, silver is not a stable material like gold, and can dissolve when in contact with food. As a result, it is not permitted by law for the dished used for food.

Alongside traditional kintsugi, modern kintsugi has become popular in recent years. Modern kintsugi has nothing to do with real kintsugi in terms of the materials used or a tradition - and should not be confused with it. The reason behind the popularization of modern kintsugi is the speed and affordability of the method. Instead of traditional, more expensive raw materials and time-consuming methods, modern kintsugi uses synthetic glues (such as epoxy) and color powders imitating gold or silver.

Modern kintsugi is an excellent way to repair objects in kintsugi style, but the similarities between traditional and modern kintsugi are limited to the appearance of the final repaired object. In general, it can be said that only traditional kintsugi and real gold can be used to repair objects intended for food or beverages.

If the price of gold is too high, it is possible to repair dishes for everyday use with traditional kintsugi, but leave the gold dust added to the repair joints. This is possible as in the end, the gold is just a decoration where the urushi lacquer is responsible for joining the parts, patching and sealing the seams.


Materials and raw materials used in kintsugi repaired items suitable for food use
When the object is to be used for food or other foodstuffs following repair, all raw materials must be safe. In traditional kintsugi, only 100% natural raw materials are used, the use of which has been studied and known to be safe.


Information about the most common materials used in kintsugi

Urushi
100% natural Japanese lacquer (urushi) made from the sap of lacquer trees (Rhus vernicifera). Urushi is highly allergenic when applied, but when dried it is a safe super material that provides a very hard, waterproof protective layer that can withstand even most acids. The only significant weakness of Urushi varnish is its sensitivity to UV radiation, which weakens its structure.

The oldest artefacts treated with urushi lacquer date back to 10,000 BC. Naturally brown-toned raw urushi (ki-urushi, seshime-urushi) is used in every stage of kintsugi repair as such, clear (shuai-urushi) or traditionally tinted to black with iron sulfide (roiro-urushi) or to red with iron oxide (bengara-urushi).

Gluten-containing flour
Gluten-containing flour is used mixed with urushi lacquer as a natural adhesive. The most commonly used flours are rice and wheat flour.

Tonoko/jinoko powder
Natural quartz mineral rich clay powder. Six types of tonoko powder are most commonly used in kitsugi, of which jinoko is slightly coarser than tonoko.

Ogakuzu
Finely ground wood powder.

Kin
Genuine average 23.75 - 24.0 carat gold dust with a gold content of 98.9 %. In order for the item to be food safe, its seams can only be finished with real gold (if the seams are finished).

Gin
Silver powder ground into a fine dust.


Starting to use a kintsugi repaired item
The repaired object can already withstand handling well, right after the last step of adding varnish and gold dust. However, the recommendation for food use is to wait another two to three months before starting the actual use, so that the seams containing urushi lacquer reach the strongest composition.


Washing kintsugi repaired dishes
Kintsugi repaired dishes cannot be washed in a dishwasher, but hand washing with diluted detergent or soap is possible. Since the gold dust is usually located on the top of the repaired seam, it is recommended to avoid strong mechanical rubbing. it is not recommended to soak kintsugi-repaired dishes in water as it may weaken the repair seams in the long run.


Heating food in a kintsugi repaired dish
After the Kintsugi repair, the dishes cannot be used to heat food in a microwave oven or an oven. Dried urushi varnish can withstand temperatures of up to maximum 100 - 120°C.

Impact and drop resistance of kintsugi repaired dishes
The ability of Kintsugi repaired dishes to withstand shocks or bumps without breaking is weaker than the original dish. Fortunately, if the seam breaks, it can be repaired again.