The chemical and physical properties of soda-lime glasses make them suitable for a visible light and hence applications. The nominally colorless types transmit a very high percentage of visible light and hence have been used for windows since at least the time of the Romans. Soda-lime glass containers are virtually inert, and so cannot contaminate the contents inside. Their resistance to chemical attack from aqueous solutions is good enough to withstand repeated boiling (as in the case of preserving jars) without any significant changes in the glass surface. One of the main disadvantages of soda-lime is their relatively high thermal expansion. Silica does not expand very greatly when heated but the addition of soda has dramatic effect in increasing the expansion rate and, in general, the higher the soda content of a glass, the poorer will be its resistance to sudden changes of temperature (thermal shock). Thus, care is needed when soda-lime containers are filled with hot liquids to prevent breakage due to rapid thermal expansion.