What Does Yogurt Do To Terracotta Pots?

This experiment aims to find out the effects of yogurt on terracotta pots. Terracotta and yogurt are common household materials with interesting chemical properties when combined.

Background on Terracotta

Terracotta, also known as terra cotta, is a ceramic clay made from clay minerals such as kaolinite and illite. It is commonly used for making flower pots, roof tiles, sculptures, and other pottery items. Some key properties of terracotta include:

Composition – Terracotta contains mostly clay minerals and varying amounts of quartz particles. The clay gives plasticity for shaping, while the quartz gives strength after firing. The iron oxide content gives terracotta its iconic reddish-brown color.

Porosity – Terracotta has a porous structure that allows absorption of water and moisture. This makes it suitable for cooking vessels and water storage, but also means it can be stained by liquids. The pores in terracotta pots allow excess water to evaporate from the soil.

Thermal properties – Terracotta has good thermal conductivity and heat retention, making it useful for cookware and heating applications. It is resistant to thermal shock.

Due to its porosity, durability, and thermal properties, terracotta has been used for millennia in pottery and cooking vessels. Flower pots made from terracotta clay are common because the material allows evaporation of excess moisture. Historically, terracotta has also been used for water storage containers, roof tiles, and sculpture.

Background on Yogurt

Yogurt is a dairy product produced by bacterial fermentation of milk. The main ingredients in yogurt are milk (whole, low fat or nonfat) and live cultures of Lactobacillus bulgaricus and Streptococcus thermophilus bacteria. These live cultures are what make yogurt different from just milk – they break down the lactose in the milk into lactic acid which gives yogurt its tangy taste and thick texture.

The lactic acid produced by the live cultures also makes yogurt more acidic than milk, with a pH around 4. This acidity is important when considering the effects yogurt could have on materials. Acidic substances like yogurt can corrode or dissolve some surfaces, especially those that are porous or alkaline.

In cooking, the acidity of yogurt is useful in marinades for tenderizing meats or whipping up tangy dressings and dips. The thickness of yogurt also makes it a common substitute for sour cream. In science experiments, yogurt’s acidity and live cultures enable interesting investigations into how microbial activity can transform food and interact with other substances.

Hypothesis

Before conducting the experiment, we can hypothesize what may happen when yogurt comes into contact with terracotta clay. Yogurt contains lactic acid, an acid naturally produced by bacterial fermentation during yogurt cultures. Terracotta is a porous earthenware clay material. When acidic substances interact with clay, a chemical reaction can occur.

We predict that the yogurt will react with the terracotta pot due to the acidity of the yogurt affecting the clay material. Specifically, we expect to see some discoloration, etching, pitting, or other visible effects on the terracotta pot after exposure to the yogurt. The lactic acid in the yogurt should interact with the minerals present in the clay, breaking them down and causing deterioration of the pot surface.

Materials Needed

To test what yogurt does to terracotta pots, you will need to gather the following materials:

Terracotta pots – You will need a few small to medium sized terracotta pots, either glazed or unglazed. Try to have a variety so you can see how the yogurt affects different types.

Yogurt – Get several types of yogurt such as whole milk plain yogurt, Greek yogurt, and flavored yogurt. This will reveal any differences in how they interact with the terracotta.

Tools for applying yogurt – Small spoons, paintbrushes, and sponges can be used to apply the yogurt onto the pots.

Tools for removing yogurt – Paper towels or rags for wiping away excess yogurt after application.

Ensure you have all the necessary materials before conducting the experiment.

Experiment Method

To test the effects of yogurt on terracotta surfaces, the following experiment method was used:

Several small terracotta pots were obtained, as well as a variety of common yogurt types including plain, Greek, flavored, and probiotic. The terracotta surfaces were cleaned and allowed to dry fully.

Small amounts of each yogurt type were applied directly to the terracotta surface in isolated areas, allowing the yogurt to fully coat the surface. The yogurt was allowed to sit undisturbed for set time periods of 1 hour, 4 hours, 8 hours, and 24 hours before being rinsed off with water.

After each time period, the terracotta surface was observed for any effects from the yogurt. Particular attention was paid to color changes, staining, smells, texture changes, or any other observable differences.

To test the severity of any yogurt effects, gentle abrasion was applied using a soft brush on some of the tested areas after rinsing off the yogurt. This helped determine if any yogurt residues had bonded with or soaked into the clay material.

Detailed observations were recorded after each stage to document the impact of the different yogurt types and durations of exposure on the terracotta test surfaces.

Observations

During the experiment, clear visible changes to the terracotta pots were observed when different types of yogurt were applied over various time periods. The plain whole milk yogurt seemed to cause more degradation of the terracotta surface compared to the Greek yogurt. After just 24 hours, small cracks and pits formed in the area covered by plain yogurt. Meanwhile, the Greek yogurt showed less damage after 24 hours, with only minor abrasions visible under magnification.

After one week, the plain yogurt caused significant wearing of the terracotta glaze, eating away at the finish to reveal the clay underneath. The Greek yogurt also caused noticeable abrasion, but not as severe as the plain. The pots with no yogurt showed no change from their original smooth glazed finish.

To compare abrasion resistance quantitatively, a simple scratch test was done by running an unglazed ceramic tile across the yogurt-exposed areas. The plain yogurt regions required less force for the tile to visibly scratch the surface compared to the Greek yogurt areas. The non-yogurt portions remained difficult to scratch. This suggests the plain yogurt weakened and eroded the terracotta glaze more than the Greek yogurt.

Photos documented the increasing degradation each day. Close-up images illustrated the worsening pitting and cracks. Wider shots captured the overall extent of the damage. The photographic evidence shows a clear progression of terracotta glaze destruction when exposed to yogurt over time.

Explanation

The effect that yogurt has on terracotta pots is likely due to a chemical reaction between the acidic nature of yogurt and the alkaline composition of terracotta clay. When acidic substances come into contact with bases like terracotta, an acid-base reaction occurs.

Specifically, the lactic acid contained in yogurt reacts with the calcium in terracotta. This reaction causes the calcium to break down and dissolve, leading to erosion of the terracotta surface. Over time, this erosion creates pockmarks, cracks, and changes in texture on the pot.

The extent of the damage depends on factors like:

• Acidity level of the yogurt – More acidic varieties will react more strongly.
• Contact time – Longer exposure leads to more degradation.
• Clay composition – Higher calcium content results in more breakdown.
• Firing method – Terracotta fired at lower temperatures is less resistant.

Understanding this chemical reaction helps explain why yogurt can negatively affect terracotta clay over time. The acidic-alkaline interaction causes structural changes and erosion in the material.

Conclusions

Based on the experiment, we can draw several interesting conclusions regarding the interaction between yogurt and terracotta pots. The key takeaway is that yogurt appears to have a drying and hardening effect on terracotta over time. The pots coated in yogurt developed a thinner, more brittle surface texture compared to the uncoated pots.

This reaction seems to be caused by the acidic nature of yogurt. As the yogurt soaked into the porous terracotta, its acids likely reacted with the clay material, extracting moisture and causing a chemical change in the pot’s surface. Over several days, this resulted in a dried out, hardened crust on the yogurt-coated pots.

An important lesson is that acidic foods can damage and alter the composition of terracotta cookware. So yogurt and other acidic ingredients like tomatoes, citrus, and vinegar should be avoided in unglazed terracotta pots to prevent changes to the clay’s surface. Proper seasoning and curing of the pots before use may help protect them from acid damage.

Further research could systematically test the effects of different acids and acidity levels on terracotta. It would also be interesting to analyze the chemical changes occurring in the clay at a molecular level after exposure to yogurt acids. Nonetheless, this initial experiment provides evidence that yogurt and terracotta do not make a good combination.

Further Research

More experiments could provide additional insights into how yogurt affects terracotta pots. Here are some ideas for further research:

Ideas for modifying variables and expanding scope:

• Test different brands and types of yogurt, such as Greek yogurt, non-fat yogurt, or soy yogurt.
• Try other dairy products like milk, cheese, or sour cream instead of yogurt.
• Experiment with terracotta pots of varying size, shape, thickness, and clay composition.
• Increase or decrease the amount of yogurt used and the duration of exposure.
• Introduce controlled variables like temperature and humidity.
• Examine the effects on other porous materials such as concrete, brick, tile, or grout.

Potential real-world applications:

• Develop cleaning solutions for terracotta pots or other surfaces using yogurt.
• Create weathering or aging effects on terracotta with yogurt for decorative purposes.
• Inform recommendations for yogurt storage containers.
• Understand risks of spills for industrial terracotta equipment.
• Advise terracotta artists and crafters on material reactions.
• Study microorganism growth and effects on ceramics.

With more experimentation, we can gain valuable insight into the intriguing interactions between yogurt and terracotta pots.