The commemorative plate made of brass is delivered together with the baby ring.
A few months or years after delivery, we have received feedback from customers saying, "It has become a bit dull," and "Perhaps because everyone in the family has been touching the plate, fingerprints have started to appear."
Brass is a metal that develops a unique texture due to surface oxidation. Over time, it can acquire an antique feel, which adds to its "character," but it can also suffer from excessive rust and darkening due to factors like skin oils, moisture, and oxidation.
Regular maintenance is necessary to keep it in good condition until the day your child reaches adulthood. 
Approximately six months ago, I received a commemorative plate from a friend family who ordered a baby ring (Thank you, T-san, for your cooperation).
After delivery, it seems that everyone in the family touched it with their hands and then put it back in the case. As time has passed, the areas that were touched by hands have become quite dark. I am thinking of actually trying to see how clean it can get.
What you need is baking soda or vinegar. Additionally, a toothbrush, a container, and kitchen paper as needed. This time, I would like to try using both baking soda and vinegar to see the actual effects.
When you search on the internet, you often come across articles that say, "Use baking soda to clean brass." Let's start by trying baking soda.
容器に重曹を入れます。
Add a small amount of water and knead it a little with your fingers.
Place the kneaded baking soda on the plate and gently rub it with your fingers.
After polishing to a certain extent overall, it's now time for the toothbrush. An old one will do just fine.
We will polish around the grooves where the engraving is located. It should take about 1-2 minutes. There is no need to polish for too long. Once you are done polishing, please rinse with water and baking soda.
This is the plate after being polished with baking soda. How does it look? The overall dullness has been removed, and it has become shiny, but the areas where fingerprints left dark marks are still stained.
Now, let's try using vinegar.
Place the plate on the container and add vinegar until the plate is submerged.
In this state, please soak for a few minutes. (Depending on the level of dirt, please adjust the soaking time. Soaking for too long can cause corrosion due to acetic acid, which may lead to darkening again.)
By the way, this time I pulled it up in about a minute.
While rinsing with water and vinegar, focus on scrubbing the areas with remaining dark stains using a toothbrush to finish up.
This is complete. It has become shiny just like when it was delivered.
The left side is before polishing, and the right side is after polishing.
If the overall dullness is mild, baking soda can be used, but if there are stubborn dark stains caused by sebum, using vinegar to scrub can significantly remove the dirt.
This time, we introduced a care method using items you have at home, but there are also cloths for polishing brass. You can find them at 100 yen shops, so it might be convenient to have one on hand. We hope you can take care of your items in an easy way.
【注意点】
○Please use room temperature water for cleaning, as the adhesive used to secure the stones can become loose (hot water and lukewarm water are not allowed). Also, be careful not to soak it in water for too long.
○ Leaving it wet can cause rust or discoloration. Be sure to dry it thoroughly before storing it in the box.
○Our commemorative plates have a matte finish on the surface. Please be careful not to polish them too much, as it may remove the matte finish.
○From around September 2023, a special treatment has been applied to the surface for oxidation prevention. Please do not forcefully clean it, especially if there are no noticeable discolorations, as the treatment may peel off.