There could be a few reasons why a T-shirt may feel loose after a few hours of wearing it and tight after washing it. Here are a few possible explanations:
Fabric Stretch: Some fabrics, particularly those with a blend of synthetic materials like polyester or elastane, can stretch over time due to body heat and movement. This stretching may cause the shirt to feel looser after wearing it for a few hours. However, washing the shirt can help shrink the fabric back to its original size, making it feel tighter.
Moisture and Heat: Throughout the day, your body perspires and generates heat, which can affect the fit of your clothing. Moisture and warmth can relax the fabric fibers, causing the shirt to stretch slightly and feel looser. When you wash the shirt, the water and detergent remove any accumulated oils or sweat that may have relaxed the fibers, allowing the shirt to regain its original shape and feel tighter.
Washing and Drying: The process of washing and drying can affect the size and fit of a T-shirt. Washing in warm or hot water, as well as tumble-drying on high heat, can cause some fabrics to shrink to varying degrees. This shrinkage can make the shirt feel tighter after washing. However, keep in mind that not all fabrics will shrink significantly, and the extent of shrinkage can depend on the specific fabric composition and care instructions.
It's important to note that different fabrics and clothing brands may react differently to wear, moisture, and washing. If you consistently experience significant changes in the fit of your T-shirts, it may be worth exploring different fabric blends or trying different brands to find the best fit and long-term durability for your preferences.