The inner lid that comes with the bottle product is a part that increases the airtightness to the point that it prevents liquid from leaking. We thought that this would minimize the deterioration of the chalk due to air.
However, we have discovered that this high level of airtightness poses the risk of the bottle exploding, so we have decided to remove the inner lids from the bottles shipped from today onwards.
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The conditions that have been confirmed to cause an explosion are a drop in air pressure and an increase in temperature.
- When I tried to open the inner lid at high altitude, it exploded and the chalk went flying everywhere.
- In a hot garage, I tried to open the inner lid after shaking it, and it exploded.
*Photo borrowed from Twitter
These are the cases we have confirmed, but Super.B clearly states to "shake well before use," and if the volume has increased due to a sudden change in temperature, there is a higher risk of it exploding, so care must be taken when opening.
Even without the inner lid, chalk deterioration can be significantly prevented by storing it in a bottle. If you have a bottle product, we ask that you remove the inner lid before using it.
(Yamamoto)