Seal Ceramics to Prevent Leaks
So you're digging through all those dusty boxes in the garage, and you come across a great piece of ceramic ware: a vase, a flowerpot, or a casserole, and you've decided to finally put it to good use. Minutes later, you notice that the reason it was boxed up is that the thing leaks like a sieve! Fortunately, your great-looking ceramic doesn't have to go back in the box, and it doesn't have to be relegated to the display cabinet. You can seal it inexpensively, with equipment you already have at home, and not detract from its value, because the sealant will be easily removable (and almost invisible in the first place). So on that winter afternoon when you have nothing better to do, seal up those ceramics and start enjoying them as they were meant to be used!
It's Easier Than You Think!
Most of what you will need you probably already have at home: a hair dryer, a hot plate, a couple of metal cans, a metal jar lid, and a couple of potholders. You will probably also need an extra person to help out if your pieces are of any substantial size. (If you are planning to serve food in your ceramics, see the second part of this article.)
If you are not planning to use the item for food, the only thing you will need to buy is paraffin wax, such as is used for making candles. Even if you are not planning to serve food in your ceramic dishes, it's best to get food-grade paraffin, because it has dozens of uses around the house, including canning and making chocolates!
Leaks are a Common Problem
Do you have ceramics that leak?
Making Your Seal
First, use your hot plate. Fill a large sturdy metal can with 3 inches of water, and place a small metal object like a jar lid or empty tuna can in the bottom, upside down. Scrape off some paraffin (it will take more than you think) into a second, smaller metal can, and place inside the first. Put the entire contraption on the hot plate and turn it on to melt the paraffin.
Get your ceramic piece and wipe down the inside with a damp rag so it is clean. When the paraffin is melted and ready for use, get a second person to hold your ceramic item with a potholder. Heat first the inside, then the outside of the pot or vase with a hair dryer until it is hot to the touch. Then quickly pour the paraffin inside, and holding the item so that the mouth is parallel to the floor, rotate it so that the paraffin touches the entire inside and will seal the item against leaks. Set the piece aside to cool (put it on a trivet or potholder).
If at some time in the future you need to remove the paraffin, it removes easily with a hair dryer. Just warm the wax up and it will peel or chip right off. Another warming, and you can wipe up any stray paraffin with a rag (dispose of the rag properly, to avoid starting a fire!).
Sealing Ceramic Cooking Dishes
If you have a ceramic casserole, glazed or unglazed, and it leaks, there is an easy fix. You simply submerge the piece in whole milk, heat gently for at least one hour, and let cool overnight. Remove the piece from the milk the next morning, and rinse. The milk will seep into the pores of the ceramic and the proteins will bond with the molecules of the ceramic dish. You will have an invisible seal and, of course, since you used food to seal it, the dish will be food-safe.
Even after you seal your ceramic baking dishes, it's a good idea to soak them in warm water for two hours before baking in them (you can dry off the insides). The water will help prevent leaks, surprisingly!
If you run your ceramic baking dishes in the dishwasher, you may need to reseal them with milk occasionally.