How to get rid of white powder, a soapmaker's pet peeve?

The white powder often appears on the side of the soap that comes into contact with the air after the soap is molded, which not only affects the aesthetics, but also requires time to remove the white powder. 

What exactly is white powder?


White powder = soda = sodium carbonate, soda ≠ baking soda, baking soda is sodium bicarbonate NaHCO₃.

Sodium carbonate, with the chemical formula Na₂CO₃, is a white powder that is easily soluble in water, and is weakly alkaline, but its alkalinity is somewhat stronger than that of baking soda.

Why does sodium carbonate (white powder) appear?


Causes: The free alkali (NaOH) in the soap that has not yet finished reacting with the oils and fats interacts with the carbon dioxide (CO₂) in the air to form the product.

From the above account, two key culprits can be identified.free alkaliOne iscarbon dioxide CO2The

So the way to avoid white powder is.Don't be an alkaline swimmer.marry sb. (of woman)Carbon dioxide (air) insulationThe

▪ What should be done then?


Avoiding the generation of white powder is not a guarantee of success, as we can only try to address the causes of the problem and make improvements.

Murderer 1: Nitrogen Free

① Beat the soap until OVER trace before entering the mold.

The principle behind this is that you want the grease to react as completely as possible with the alkali, the longer and more evenly you beat it, the better the saponification should be, and with less free alkali, the CO2 won't have a chance to get to it.

②Reduce the amount of dissolved alkali.

The more water in the soap, the more opportunities for water molecules with free alkali evaporation to the surface of the soap, but the amount of water is often a key factor in adjusting the rate of saponification soap, so the amount of water in the end to catch how much, the novice does not recommend less than 1.8 times, but still depending on the speed of the individual soap and the recipe discretionary adjustment.

③ Do not let the soap body sweat.

Into the mold after the saponification reaction continues to take place, the soap body temperature rises gradually, you may have to keep warm (put the soap in a polycarbonate box) or some additives caused by the soap body temperature soaring, coupled with the environment stuffy ventilation, you will see the soap surface sweating, sweat beads is the water in the soap body, the same as the second point, water with the free alkali out of the beads of sweat dry or you wipe it off, the white powder will also appear with the. If the soap mold is covered or sealed with plastic wrap, you can wait for the soap to solidify and then open a small opening to ventilate.

④Do not dehumidify or put in an air-conditioned room for unmolded soap or even freshly molded soap.

It is also related to the fact that water molecules travel with free alkali.
Avoid lowering the ambient humidity when the soap still contains a lot of water, as the obvious difference in humidity between inside and outside the soap will cause the water molecules to carry the free alkali from the high humidity to the low humidity again, yes! Another gorgeous encounter.
This is also the reason why we sometimes say that we should not take off the mold too early.
Another reason not to demold too early is the temperature difference.

⑤ Avoid temperature difference.

Saponification is exothermic and can peak at 40-50 degrees, so it's safe to assume that any soap that hasn't cooled down completely should be warmer than room temperature.
At this point the water molecules will run from the hot to the cold..., yes! The thing you don't want to see is happening again!
So often you will hear soap friends say, put in the incubator soap do not always lift the peep, you gave it the temperature difference, the white powder will grow to you. In addition, the soap body is still warm, do not rush to take off the mold, is also the same reason.

Murderer 2: Carbon Dioxide

(6) Insulate the soap from the air by covering it with a lid or sealing it with plastic wrap.

It sounds like a good idea, but it would be nice if it were that simple!
If you have a full mold, it's hard to seal the plastic wrap because it will damage the surface of the soap (the plastic wrap will stick to the soap), unless you have a soap mold with a wooden box with a lid, then you don't have this problem.
However, there are a lot of buts in life. In summer, the temperature is high, so if you like to add a lid or seal the film, it may cause the soap to freeze or volcanic eruption (soap cracking), and this method depends on the ambient temperature.

(7) Spray 95% of alcohol on the surface of the soap.

This is also a way to insulate the soap from air, as the alcohol accelerates saponification. When a thin layer of solid soap is formed on the surface of the soap quickly, it prevents the formation of white powder from air contact, but you must wait until the surface of the soap fogs up a little before spraying.
Although this method can reduce the production of white powder, but the surface has traces of spray, may need to improve the nozzle, so that the water molecules sprayed by the sprayer is as fine as possible, and to spray evenly.

What should I do if I still have white powder even though I have ruled out all of the above conditions?


①The most common practice is to use a soap trimmer to shave, and the shavings or filaments are collected and used as laundry detergent.
However, if the area where the white powder grows is not a flat soap surface, it is impossible to plane it.

②For non-flat soap surfaces, use a lint-free cloth to rub the white powder off when the soap is still slightly moist. However, if the white powder is too thick, it will be very hard to grind, and the white powder is too thick, which means that the soap is not saponified evenly and completely.

③ Steam it with the ironing steamer: because sodium carbonate is soluble in water, the white powder will disappear when the surface is steamed with hot air, but the surface of the soap has become soft and wet, and there will still be traces of steaming even after drying.

Many people say that you don't need to remove the white powder from your own handmade soap. Although sodium carbonate is weakly alkaline, it may be irritating to people with sensitive skin, so if you don't want to remove it, you can rinse it in hot water before using it to dissolve the white powder on the surface (the principle is the same as steaming it over with hot air).

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