What is a Bath Bomb?

Bath bombs, also known as effervescent bath pills, are products designed to add colour, fragrance, and fizz to a bath. Recently, they have surged in popularity, with numerous variations available in retail and online stores. The chemistry of bath bombs is relatively straightforward, involving an acid-base reaction between citric acid and sodium bicarbonate. (1).This combination, when dry, remains inactive, but upon contact with water, it reacts to produce carbon dioxide, salt, and water. For example, sodium bicarbonate and citric acid react in the presence of water to create this effervescent effect (2).In today’s fast-paced world, achieving a relaxed state of mind and body can be challenging. Bath bombs offer an affordable means to support both mental and physical health. Through the use of moulds and dyes, herbal therapeutic bath bombs can be customized in various shapes, sizes, and festive colors, adding a playful and enjoyable element to bath time(3).

Objective of the Study

The objective of this study is to design bath bombs that capitalize on their medicinal and cosmetic properties, such as body cleansing, detoxification, and moisturizing. This involves assessing the safety and stability of these formulations, including pH levels and antimicrobial activity, to ensure they meet quality standards suitable for consumer use (3).

Reaction

Citric Acid + Sodium Bicarbonate + Water =Salt+ Water+ CO2

This reaction produces sodium citrate, water, and carbon dioxide. The carbon dioxide generates bubbles in the water, and the formulation's scent is released. A surfactant foaming agent creates additional foam, enhancing the bathing experience. Because the ingredients are diluted in water, sodium bicarbonate and citric acid do not cause skin irritation (2).

Cosmetic Chemistry

Educators continuously seek innovative ways to connect chemistry to real-world applications, often through food, medicine, and increasingly, cosmetics. The cosmetic chemistry industry, valued at over $100 billion, produces a range of products from shampoos to perfumes. Despite its everyday relevance, there are limited teaching experiments related to cosmetic chemistry in general courses. Notable educational activities include making cold cream, lotion, and soap, and exploring the acid-base properties of bath bombs. This study provides an experiment where students can create and analyse bath bombs, integrating fundamental principles of kinetics and cosmetic chemistry (1).

Introduction to Skin

The acidity of the skin's surface was first discovered by Heuss in 1892. Subsequent potentiometric measurements have shown that the skin's pH ranges from 4.2 to 5.6. The use of glass electrodes for skin pH readings has become common since the early 1950s. Various factors influence skin pH, including endogenous factors like age and sebum, and exogenous factors such as detergents and cosmetic products (4).

Sodium Bicarbonate (Baking Soda)

Sodium bicarbonate offers several skin benefits, such as exfoliation and pore tightening. It helps remove dead skin cells, leaving the skin smooth and glowing. Additionally, it neutralizes body odors, making it an ideal ingredient for fragrant bath bombs (5).

Corn starch synergistically enhances the effects of other bath bomb ingredients like baking soda, prolonging the effervescence. This results in a longer-lasting fizz, adding to the overall bathing experience (5).

       
           
       
    Fig No.2- Corn Starch.

Epsom salts, composed of magnesium and sulphate ions, are easily absorbed through the skin. They play critical roles in, inflammation reduction, muscle relaxation, and preventing arterial hardening. Sulphate in Epsom salts also help treat headaches (6).

Neem oil, from the Meliciaceae family, is used to treat various skin issues, including wrinkles and erythema. Its antibacterial and moisturizing properties make it a common ingredient in external cosmetic applications (7).

Rose oil (Rosa damascena Mill, Rosaceae) is valued in medicine for its therapeutic properties, particularly in aromatherapy. It alleviates emotional distress, anxiety, tension, and stress-related insomnia. Rose oil also exhibits antimicrobial properties (8).

       
           
       
    Fig No.5- Rose oil

Turmeric

Turmeric, derived from the rhizome of a ginger-like plant, contains curcumin and volatile oils with strong anti-inflammatory properties. Both in vivo and in vitro studies have demonstrated turmeric's ability to inhibit the activity of various carcinogens and mutagens. It also inhibits the growth of numerous bacteria, parasites, and fungi (9).

       
           
       
    Fig No.6- Turmeric

Citric Acid

Citric acid, found in citrus fruits, is a tricarboxylic acid with a molecular weight of 210.14 g/mol. It is safe, affordable, biodegradable, and used for its sequestering, buffering, wetting, cleaning, and dispersing properties. Citric acid is essential in producing effervescent salts, confections, soft drinks, and medicinal citrates (10).

       
           
       
    Fig No. 7 Citric Acid

Formulation Table

       
           
       
    Table no. 02. Formulation table of bath bombs

Citric Acid + Sodium Bicarbonate + Water = Salt + Water + CO2

METHODOLOGY

Preparation of Bath Bomb

A. Step One

1. Weigh all dry ingredients.
2. Add them to a dish and stir.

B. Step Two

1. In a beaker, mix turmeric with rose oil.
2. Add rose water to the turmeric solution.
3. Slowly mix the liquid into the dry ingredients until slightly moist. Avoid adding too much water to prevent premature neutralization. Press the mixture into moulds and freeze for 30 to 45 minutes (11).
4. Evaluation Tests

Physical Appearance

Physical appearance was assessed for three formulations (A, B, C) (7).

Effervescent Time

The effervescence time was measured by placing a bath bomb in 500 ml of room temperature distilled water until bubbling ceased (7).

The bath bomb was dissolved in a tub of water, and the test was considered successful if no irritation occurred after five minutes (7).

The pH of the solution containing the bath bomb was measured (7).

Stability Testing

Samples were stored at room temperature for two weeks, and any changes were noted (7).

Nutrient agar was prepared aseptically, and Staphylococcus aureus was used to test microbial growth. Three testing methods were employed

Negative control testing:

Nutrient agar was weighed, dissolved in distilled water, and placed into a petri dish.

Positive control testing:

Positive control testing involved weighing and dissolving nutrient agar in distilled water, then adding bacteria to the medium and pouring it into a petri dish.

Testing with bath bombs:

Nutrient agar was weighed and dissolved in distilled water before adding bath bombs formulation to the medium and pouring it into a petri plate.  These methods were used to assess microbial growth with Staphylococcus aureus as  the bacteria and nutrient agar as the culture medium (12, 13).