Marks inside a bottle can make a small box of cleaning tablets look tempting. Before buying, ask two practical questions: does this treatment fit my bottle, and can I leave it open while it works? Those answers matter more than picking a cleaner by the word “stainless” on the front.
I’m Irene, a Taiwan-born pharmacist qualified in Japan.
Japanese official information checked: 25 October 2026. One product: Kobayashi ステンレス水筒洗浄中, 8 tablets.
Check the bottle before the cleaner
Keep following the care instructions for your exact bottle. The material list below is the cleaner maker’s stated scope, not permission to treat every bottle or coating. If the two sets of instructions do not clearly fit together, ask the bottle maker before purchasing or using the tablets.
| Check | What the manufacturer states |
|---|---|
| Listed use | Interiors of stainless-steel, plastic, ceramic and fluorine-coated bottles or cups |
| Do not use on | Aluminium, copper, brass, iron, or items with gold or silver decoration |
| Still unresolved? | This guide does not establish exterior, lid or gasket treatment. Follow the exact vessel’s instructions. |
On a phone, swipe the table sideways to read the full checklist.
The maker describes treatment of staining, including polyphenol-related deposits. It cannot remove discoloration of the material itself caused by heat. A remaining mark is therefore not a reason to keep increasing the treatment time.
Prevent mistaken drinking or eating. Use only for the stated purpose, and keep the tablets and treatment setup out of the reach of children and people with dementia.
Wear rubber gloves if your hands are prone to irritation or roughness.
Look for the full Japanese name and 8錠
Match ステンレス水筒洗浄中 and 8錠. This is one box of eight tablets; the number of tablets in the box does not tell you how many fit your particular bottle. The package’s promotional wording is the manufacturer’s, not an independent guarantee from Irene.
Three steps, with the lids left open
1. Match the water amount and temperature
Use one tablet per 350 mL of water, at approximately 40°C. Never use water at 60°C or higher. Fill the vessel fully in a place where overflow is acceptable, then add the appropriate amount of cleaner. Open the inner packet only when ready, and use it immediately.
For a different volume, do not guess a rounded dose or split a tablet from this guide. Check the current package or ask Kobayashi when the amount is unclear.
2. Leave it open and mark it as cleaning
Keep the lid and inner lid open for about two hours; the maker allows overnight treatment for heavy staining. Put the supplied 洗浄中 sticker somewhere conspicuous to prevent accidental drinking.
3. Rinse the interior thoroughly
After treatment, rinse the inside thoroughly with water. Gently use a sponge on remaining dirt; gently rub off any undissolved residue.
Pouring out the liquid is not the whole final step. The small drawing shows emptying; the required thorough rinse is explained in the text. Continue with your bottle’s own care instructions rather than borrowing a method for another vessel.
Put the remaining tablets away safely
- Store away from direct sunlight, heat and humidity, out of the reach of children and people with dementia.
- Follow local packaging-disposal rules. Ask your municipality about disposing of unused contents; do not improvise a neutralising or drain-disposal method.
If the cleaner gets into eyes, mouth or onto skin
The following is Kobayashi’s product-specific first-aid guidance, including its current FAQ that explicitly lists this cleaner. It is not a general recipe for all household chemicals.
- Eyes: do not rub. Immediately rinse under running water for at least 15 minutes, then promptly see an ophthalmologist with the product. Do not wait for symptoms before seeking eye care.
- Human mouth or swallowing: remove remaining product from the mouth. Do not induce vomiting; rinse the mouth. The FAQ states one to two cups of water or milk and observation; if anything is abnormal, take the product to a doctor of internal medicine.
- Do not force someone to drink or treat that quantity as a child’s weight-based dose. If someone cannot swallow safely, or you are unsure what to do in an actual accident, seek immediate professional advice.
- Skin: wash immediately with soap, then rinse thoroughly with water or lukewarm water. If abnormalities remain, take the product to a dermatologist.
- A pet puts it in its mouth: do not force vomiting. Contact a veterinarian immediately and follow their directions; do not give the human water-or-milk quantity to a pet.
Before putting the box in your basket
Have the bottle’s care instructions, its water volume and a suitable place to leave it open in mind. If any of those is unanswered, resolve it first. A useful cleaner purchase starts with a method you can follow, not an assumption that one tablet suits every bottle.
Official sources and image credits
The cover and article’s package photo and procedure drawings come from Kobayashi Pharmaceutical’s product page. Image rights remain with Kobayashi Pharmaceutical or their respective rights holders; attribution does not imply permission or endorsement.
