Subject:Re: Old, small oriental vase with no markings
Posted By: Bill H Mon, Nov 05, 2018
The crackle under the glaze indicates your vase is made of soft-paste pottery or stoneware, not hard-paste porcelain, which is vitrified to the point of being another form of glass. The soft-paste is vulnerable to some of the harsher detergents and household cleaners that tend to dissolve calcium exposed by the crackle.
If you can take the necessary precautions, I would suggest you use a mixture of mild dishwashing detergent and 40-percent hydrogen peroxide gel diluted with tap-water. The 40-percent hydrogen peroxide is available here in the USA at beautician supply outlets for use in producing platinum blondes at beauty salons, and it may also be found in the same venues where you live. However, it isn't sold in large amounts or concentrations due to the possibility of it being used in homemade explosives and other potential safety problems.
You'll need a sturdy, chemical-resistant plastic bowl, and a pair of rubber gloves when mixing, immersing objects and rotating them. The peroxide in such high strength is quite harmful to skin and other organic materials. You'll need about a cup of peroxide, a quarter-cup of detergent and a quart of room-temperature water. Mix it well using a rubber spatula or large stainless steel spoon, stirring gently so as not to splash any on yourself. Rinse utensils well after use.
Once the solution is well-mixed, rinse off the vase and place it wet into the solution on its side, allowing the interior to fill. If part of the vase is exposed, no problem. You can either spoon some of the solution onto the exposed side and then rotate it every few hours to its opposite side (using the rubber gloves again).
Usually, a 24-hour day in such a bath will get rid of most organic material, though the mouth rim, where the glaze is fritted, might benefit from gentle brushing with a soft toothbrush.
Be sure to rinse leftover solution down the drain, without using the garbage disposal at the same time. Be sure to use the rubber gloves when doing this and cleaning the mixing bowl. If you have young children in the house, please make sure you have a place secure enough for this job so they will not be in danger. Otherwise, just settle for cleaning the vase superficially with the mild detergent and a soft toothbrush, and leave the peroxide alone.