Terra cotta is a porous material, which means that when it is wet, liquids and tiny particles may pass through the substance and into the pot. The salts and minerals that are found in the soil inside the container are picked up by the water as it moves through the pot, causing parts of the container’s outside to become white and chalky. After the pot has dried, these blemishes stand out much more prominently. This discoloration may be eliminated, therefore there is no need to throw away the pot just because there is white powder in it.
Salts and minerals that are included inside fertilisers are able to be taken up by the ground, particularly when there is moisture present. Some of these salts and minerals may find their way inside the pot over time, particularly if the soil has been over-fertilized, and they may ultimately work their way through the whole container, emerging on the outside.
Hard Water Deposits
Because the minerals in tap water, including calcium, have the potential to deposit themselves on surfaces subjected to evaporation, things like shower heads and spigots may occasionally be seen to have a white residue on them. Terra cotta undergoes the same process, in which it absorbs both the water and the minerals that are contained inside it. The minerals are left behind when the water evaporates, giving rise to the white powder you see here.
Preventing White Powder
It is possible to avoid chalky residue from forming on the outside of terra-cotta pots by watering the plants with rainwater or distilled water rather than tap water. Leach the soil if the same plant has been in the pot for more than six months by pouring enough water to equal twice the volume of soil through the pot. For best results, use rainfall or water that has been distilled. Before beginning the leaching process, it is important to remove any white residue that has been seen on the soil’s surface. This will prevent minerals from working their way into and through the terra cotta. Brushing the surface of the pot is often sufficient to remove the white deposits that have accumulated there. To protect the surface of the pot from being marred, start by using a brush with nylon-based bristles, such as one that is designed for cleaning domestic surfaces. Follow up with a wire brush, take care not to push too hard in case the pot is soft enough to reveal scratches or damage.
Brush it Away
After brushing, remove any remaining residue from the pots by combining water, rubbing alcohol, and white vinegar in equal amounts, then applying the solution to a sponge and wiping it all over the inside and exterior of the pots. While the alcohol assists in cleaning the pot, vinegar is used to dissolve the minerals.
Clean off what’s left of the residue after brushing by mixing equal parts water, rubbing alcohol and white vinegar, then rubbing it over the pots inside and out with a sponge. Vinegar dissolves the minerals while alcohol helps clean the pot.