Typical mistakes of a kintsugi beginner

Kintsugi is not an easy technique.

There are many points in the series of process that beginners can easily get tripped up on.

This article describes common mistakes and countermeasures.

 

 

Failures that CANNOT be recovered

There are two types of failures in kintsugi: "recoverable" and "irrecoverable.

First, here are some examples of "irrecoverable" failures.

Nevertheless, all of them can be prevented with advance measures, so be sure to check them before you work.

1. Misalignment during gluing

This is one of the most common mistakes in kintsugi that cannot be undone.

There are several causes of misalignment at the time of gluing.

 

(1) Already misaligned at the time of bonding.

This occurs when the Mugi-urushi is thickly coated or gluing pieces together without crimped.

The more pieces you glue, the more likely they are to shift.
Make sure to check the edges are not shifting every time you glue one piece, and then fix it with masking tape.

 

(2) Gradual displacement after gluing

This is likely to happen with the porcelain.
It is caused by gravity causing the cross section to shift little by little.

As a countermeasure, fix it firmly with masking tape.

For flat dishes, it is also effective to store them in a vertical orientation, which prevents them from shifting even when subjected to gravity.

 

2. Stains on the surface of the ceramics

If the urushi gets on the surface of thin glazed or white ceramics, it may leave stains.

If the pottery has a solid glaze, the stain can often be cleaned off by wiping it off with ethanol or scraping it off with a cutter.

However, thin glazed ceramics, for example, can often not be recovered unless measures are taken against stains in advance.

As a specific measure, it is effective to work with masking tape around the seams.

Particular attention should be paid to the process of gluing.

It is a common mistake to get mugi-urushi on your hands while working, which becomes stain when touching the ceramics as it is.

It is a good idea to protect areas that are likely to be stained with tape, not just around the seams.

Please refer to the tutorial for specific processes.

 

3. Stains on the inside of the ceramics

This is also a type of urushi stain.

However, while the stain introduced earlier was caused by urushi getting on the “surface” of the ceramics, this is caused by urushi staining the “inside” of the ceramics.

This is often seen on white ceramics, especially on kohiki (powder-coated) pottery and soft white clay porcelain.

Since this is caused by urushi staining on the inside, it does not matter whether the surface glaze is firm or not.

Once a stain is formed, it cannot be removed, so it is important to take countermeasures in advance.

Countermeasures include soaking nikawa or egg white into the substrate in advance, or "Medome" with starch to reduce the penetration of urushi.

 

Failures that CAN be recovered

The following are examples of "recoverable" mistakes.

It is possible to get it back, but it is recommended to check before the work is done as it may cause more work and rework.

1. Gold powder does not shine even when using cotton ball.

There are three main reasons for this.

When reapplying gold powder, wipe off the seams with ethanol and apply Bengara urushi again.

 

(1) Bengara urushi is not applied thinly enough

If the Bengara urushi is not applied thinly enough, the gold powder will sink into the Bengara urushi even if it is applied.

 

(2) Bengara urushi has been rubbed with cotton

The important thing when using cotton is not to apply the cotton itself to the bengara urushi.

Be careful not to press the cotton hard or apply gold powder without creating a flat surface free of fluff.

 

(3) Less gold powder on the cotton ball

When applying with cotton, it is ideal to make sure that only the gold powder on the cotton touches the bengara urushi.

For this reason, it is very important to make sure that the cotton contains plenty of gold powder.

If it is difficult to use only cotton ball, you can apply gold powder more safely by using Ashirai brush. 

 

2. Mugi-urushi does not harden

There are four main reasons why mugi-urushi does not harden.

When gluing again, remove all the pieces, wipe off the Mugi-urushi on the cross section thoroughly with ethanol, and start by applying mugi-urushi.

If the mugi-urushi is partially hardened, remove it with a cutter.
 

(1) Low temperature during storage

Not only humidity but also temperature is an important factor in the hardening of urushi.

In some cases, even if the ceramics are stored in cardboard boxes with wet towels after work, they may become cold at night while waiting overnight, and the urushi will not harden sufficiently.

In particular, the storage environment for 12 hours after work has a great influence on the hardening of urushi, so it is recommended to work in the morning if possible, so that the temperature does not drop as much.

(2) Salt or oil on the ceramics

When salt or oil is mixed with urushi, it dries extremely slowly.

If there are still stains on the ceramics, wash it once with detergent or ethanol and dry it thoroughly before repairing.

(3) Excessive application of masking tape

For mugi-urushi to harden, it must come into contact with air.

Therefore, if the joints are blocked with tape, the mugi-urushi may not harden.

When fixing pieces with the tape, be sure to apply the tape at intervals.

(4) Thick coating of mugi-urushi

If the mugi-urushi is applied thickly and glued together, excess mugi-urushi will protrude from the joints, making it difficult for the inner mugi-urushi to come into contact with air.

This can cause only the surface of the mugi-urushi to harden, leaving the inside soft.

When applying mugi-urushi, it is best to apply it thinly or to remove the excess mugi-urushi with a bamboo spatula after gluing.

 

3. Sabi-urushi or kokuso-urushi does not harden properly

There are four major reasons why sabi-urushi or kokuso-urushi does not harden.

When redoing the work, wipe off Sabi-urushi or kokuso-urushi with ethanol and reapply the them again.

If Sabi-urushi or kokuso-urushi has hardened in some areas, remove it with a cutter.

(1) Low temperature during storage

Not only humidity but also temperature is an important factor in the hardening of urushi.

In some cases, even if the ceramics are stored in cardboard boxes with wet towels after work, they may become cold at night while waiting overnight, and the urushi will not harden sufficiently.

In particular, the storage environment for 12 hours after work has a great influence on the hardening of urushi, so it is recommended to work in the morning if possible, so that the temperature does not drop as much.

(2) Salt or oil on the ceramics

When salt or oil is mixed with urushi, it dries extremely slowly.

If there are still stains on the ceramics, wash it once with detergent or ethanol and dry it thoroughly before repairing.

(3) Using sabi or kokuso urushi that has begun to dry

Pastes mixed with Tonoko, such as sabi-urushi and kokuso-urushi, easily evaporate moisture and quickly become dry.

If you use a paste that has begun to dry out, it will easily peel off after it hardens.

If the paste has dried, wipe it all off once and remake it again.

(4) Thick coating

If sabi or kokuso-urushi is applied too thickly, the inside of the paste becomes inaccessible to the air.

As a result, only the surface of the paste hardens, leaving the inside soft.

Adjust the thickness of kokuso-urushi so that it is no thicker than 2~3mm, and for sabi-urushi, no thicker than 1mm.

 

4. Black or bengara urushi does not harden properly

There are there major reasons why black or bengara urushi does not harden.

When redoing the work, wipe it off with ethanol and reapply the them again.

If it has hardened in some areas, remove it with a cutter or abrasive sheet.

(1) Low temperature during storage

Not only humidity but also temperature is an important factor in the hardening of urushi.

In some cases, even if the ceramics are stored in cardboard boxes with wet towels after work, they may become cold at night while waiting overnight, and the urushi will not harden sufficiently.

In particular, the storage environment for 12 hours after work has a great influence on the hardening of urushi, so it is recommended to work in the morning if possible, so that the temperature does not drop as much.

(2) Oil left on acrylic plates and brushes

When salt or oil is mixed with urushi, it dries extremely slowly.

If there are still oil left on the acrylic plates and brushes, wash it with ethanol before working.

(3) Thick coating

If bengara or black urushi is applied too thickly, the inside of the urushi becomes inaccessible to the air.

As a result, only the surface of the paste hardens, leaving the inside soft.

Adjust the thickness of bengara or black urushi so that it is no thicker than 1mm.

5. The area where gold powder was applied turns red

This is due to the fact that the gold powder has sunk into the bengara urushi because the coating of bengara urushi was too thick.

Basically, additional application of gold powder will stop the sinking, but in some cases it sinks slowly, so it is better to keep a close eye on it for at least 10 minutes.

 

6. Wrinkles have formed in black or bengara urushi

Wrinkles that occur during the primer and middle coats can be caused by two main reasons.

If wrinkles have formed, it should be scraped off with an abrasive sheet that will not scratch the ceramics, or scraped off with a cutter and reapplied again.

(1) Excessive humidity during storage

Humidity is necessary for urushi to harden, but black or bengara urushi will not harden properly if the humidity is too high.

Specifically, if the humidity exceeds 80%, the wrinkles tends to be formed.

If possible, reduce humidification a little or store the ceramics slightly away from humidification sources to keep the humidity around 60~70%, which will prevent wrinkles.

(2) Thick coating

Thick coats of black or bengara urushi may cause wrinkles , even if the humidity is maintained properly.

Especially in areas with large chips, shrinkage is more likely than usual, so it is necessary to apply a thinner coat or reduce the humidity.

However, this is a point that is difficult for beginners to control, so it is recommended to scrape off the wrinkles as they appear.

 

If you are not sure how to proceed

What I have described so far are common failures, and there are many other cases.

The best way to deal with the situation may vary depending on the type of ceramics and the damage, so there may be cases that do not apply to the ones described in this article.

If you are not sure how to proceed, please contact me through the Kintsugi Forum and I will be able to answer your questions to some extent.