Aluminum foil is a good thermal insulator because it reflects radiant heat, prevents convection, and reduces thermal conduction. In other words, it acts as a barrier that traps air and prevents the transfer of heat from the outside to the inside or vice versa. Therefore, when aluminum foil is added to the interior of a lunch bag, it helps maintain the temperature of the food and drinks inside by preventing heat from entering or escaping.

Washable kraft paper, on the other hand, is a material that is durable, water-resistant, and easy to clean. It is made from natural cellulose fibers that are stretched and compressed to create a strong and dense material that can withstand daily wear and tear. When combined with aluminum foil, washable kraft paper creates a practical and functional lunch bag that can keep food and drinks fresh and at the right temperature.

In summary, the insulation effect of aluminum foil in washable kraft lunch bags is important because it helps maintain the temperature of the food and drinks inside the bag. This is reflected in the choice of materials for the lunch bag and its design, which prioritize functionality and durability while still being environmentally friendly and easy to clean. So, lunch bags made with washable kraft paper and insulated with aluminum foil are a popular choice for those who want a sustainable and practical option for carrying their meals on the go.