Weight of a soap may not be exactly what it is in the label. When you are labeling a soap, one of the main problems is to note the net weight since it continues s to vary with time due to the evaporation of water, starting with the minimum limit of 33%. The bar soaps that are processed at homes usually contain a lot of water. They look like a pancake batter at their earlier stage. But once the thing hardens enough to withstand 3 or 4 days then 25% of water remains. Therefore, it is hard to tell what is the exact weight of bar soap.

Typically a bar soap weighs somewhere around 120 grams. However, this can change between products and moisture loss of the soap over a period of time.

So when a customer is buying a product, its weight may not be more than the one stated on its label, especially in case of a bar soap whose weight changes with time. These are some factors that affect the weight of bar soap.

The time when the soap was packed and when it was sold

In this case, the time is directly proportional to weight loss i.e. when the soap is packed right after its preparation then weight loss will be significantly less or none. However, if the case is opposite then you will certainly find a significant change in its weight.

The environment in which the soap was placed

Observe and record the environment in which you have stored the soap before its packaging. If the atmosphere is damp and humid then the soap will remain wet resulting in a gradual increase in weight. However, if it is kept in a dry environment then the water present in the soap also dries and reduces its weight. So a stable environment must be provided while storing a bar soap i.e. neither too humid nor too much dry if you want to keep its weight unchanged.

As mentioned earlier that the weight of the soap does not remain same all the time. So it is better to note it time to time if you are curious about how much exactly your bar soap weighs. You can calculate it by using the formula given below:

The formula

{1-(C-P)/O} x 100= WL %

In which:

C indicates the current weight

P represents the packaging weight

O symbolizes the original weight

WL is defined as the weight loss

How to use this formula

Here is the step by step process to make it easy for you:

• The first step is to note down the exact dimensions and plug them in:

For example if:

C= current weight= 4.6 oz.

P= packaging weight= 0.1 oz.

O= original weight= 5.0 oz.

{1- (4.6-0.1)/5} x 100

• Number 2, make calculations, one at a time:
• {1- (4.6 – 0.1)/ 5.0} x 100
• {1- 4.5/5.0} x 100
• {1 – 0.9} x 100
• {0.1} x 100
• 1 x 100
• 10% Answer

So it means your bar soap has lost 10% of its weight due to the evaporation of water.

Weight Loss from Water Evaporation

Soaps get lighter and smaller with the passage of time mostly due to the evaporation of water. However, some additions like essential oils can also evaporate water. Overall, the bulk of the weight loss is from an evaporation of the amount of water remaining in the soap. So calculating the net weight over time help us to determine what remains in the soap when all, or nearly all, of the water is gone.

Determining the net weight of the bar soap

In order to determine the net weight follow the steps given below. However, this will give you the lowest possible weight for your soap

• Take a bar of soap (or number of bars, to calculate an average amount) and weigh each right after you uncover it and trim (before any drying or dampening takes place).
• The multiply that amount by the percentage of water you obtained by using the formula mentioned earlier.
• Subtract the water amount from the total weight.

If you are not able to understand the thing from these points then have a look at the procedure given below, this will help you surely!

According to the above given information we have:

C= 4.6 oz.

P= 0.1 oz.

O= 5.0 oz.

And we got 10% as an answer after using the formula {1-(C-P)/O} x 100= WL %

And now for a net weight, we will form the equation depending on the amount calculated above and use it that is:

{1- (4.6 – 0.1)/ 5.0} x 100

• x 100

As the formula says

{1-(C-P)/O} x 100= WL %

So

• x 100 = 10%

As we know that

% means 1/100

Therefore,

• x 100 = 10 x 1/100

Which gives us:

1 oz.

So it means the bar soap has lost minimum 1 oz. at the moment.

Net Weight Rules

Keep this fact in your mind that the net weight written on the label of a product can never be more than its actual net weight, however it can be less.  In simple words, the consumer can get more than they expect, but never less than they expect (since they believe mostly the details written on the label).

Therefore, the safest bet is to go with the lowest possible net weight, because in this way nobody will doubt what you are selling.

How to calculate changes overtime

If you want to know that what the weight of your soap will be in 30, 60, 90 or more days, you need to make the calculations over time (and keep records). Kindly, go through the steps given below for that:

• Record the dimensions right after you unpack it
• Weigh the bar soap you have purchased after 30 days again
• Note the average weight loss, number of days and individual weight loss.
• Keep track of the time and weight of the packaging because it will probably affect the rate of weight loss.
• Repeat the procedure again after 60 days
• If your soap is sold in 90 or more days before, continue to weigh the test bars every 30 days (1 month), this will help to find the factors like what keeping them from being sold.