Old terracotta pots are easy to obtain second-hand, but many of them have stains, chips, or become worn down from years of previous use. Figuring out a way to refurbish such pots can be a challenge that can lead you down a Pinterest rabbit hole. Older terracotta pots are denser than new ones, which are ever increasingly becoming more porous and consequently more prone to chipping and cracking.
The central challenge in refurbishing terracotta is overcoming the porousness of the clay. While this porousness is appealing because it provides breathability and balances the moisture for the plant roots, it is this absorption of moisture that prevents many suggested ways for refurbishing pots from being permanently successful. There are many craft-type projects for terracotta pots such as sticking fabric on them or gluing buttons on them, but these are better suited for plants that require minimal moisture or pencil holders. Very few suggestions provide ways to alter the surface of terracotta for durable outdoor use.
Many crafters interested in revitalizing terracotta recommend using acrylic paint as the easiest method for adding colour and water resistance to terracotta. However, to prevent the paint from bubbling or peeling off in a short amount of time, it is necessary to coat both to the interior and exterior surfaces of the pot. Thus, any notion of painting a partial design on the pot, and leaving the underlying terracotta exposed, will be short-lived. While this could get extend the use of the pot in a bearable way because it is more aesthetically pleasing, when the time comes to finally dispose of the pot, the acrylic waste will only compound what is going into waste streams.
Pots get knocked around and weathered by the elements on the outside, and worn down by moisture and plant roots on the inside. All it takes is a small scrape in the paint seal for terracotta to start absorbing moisture again. Acrylic paint is basically liquid plastic, so coating and decorating terracotta is basically applying a plastic film in order to prevent it from doing what it is naturally inclined to do is a fool’s errand. It is akin to expecting rubberboots made from a single layer of cling-film to survive your romp through the puddles down a muddy lane. If using acrylic to add a dash of colour to a terracotta pot, it will be best applied above the soil line once planted, so at least gravity works in favour of draining the moisture away, and the properties of the terracotta can still do their magic at root level.
Unless you can glaze and fire terracotta, any other coating is temporary solution. The best thing to do is either celebrate the imperfections as in Japanese kintsugi (gold filling), grind out small imperfections with sandpaper, or use grout and mosaic tile the pot.
Grout, as it functions in a tiled shower, does not absorb moisture, but needs other components (i.e. tiles) to strengthen its integrity. Unsupported grout coated terracotta will crack and break away from the terracotta like an eggshell after time and exposure. Using broken vintage dishes can provide the same support as tiles provided that the unglazed edges are beneath the grout. Similarly, using drywall tape or some mesh-like remnant within the grout will also provide structural integrity for increased durability. The pots will likely not survive outside in the winter below freezing temperatures, however, this method can make use of multiple reclaimed items. Grout adds weight to the pot, but the advantage of the weight prevents the plants from being blown over in high winds.