The soaking time for a whetstone can vary depending on the type of whetstone and the manufacturer's recommendations. Generally, whetstones are divided into two categories: oil stones and water stones.

Oil stones, as the name suggests, require the use of oil as a lubricant during sharpening. These stones do not require soaking. Instead, they should be periodically lubricated with honing oil or mineral oil before and during use.

Water stones, on the other hand, are designed to be used with water as a lubricant. These stones typically require soaking before use to ensure proper hydration. The soaking process helps the stone absorb water, which improves its cutting efficiency and prevents it from drying out too quickly during sharpening.

The soaking time for water stones can range from a few minutes to around 10-15 minutes, depending on the specific stone. It is important to follow the manufacturer's instructions for soaking time, as different water stones may have different requirements. Over-soaking a water stone can cause it to become too soft or degrade its performance.

After soaking, excess water should be poured off, and the stone should be placed on a stable surface or a stone holder for sharpening. Some water stones may require periodic rehydration during use, with water sprayed or dripped onto the surface to maintain the desired level of moisture.

It's worth noting that there are also synthetic whetstones available that do not require soaking. These stones are designed to be used with water or can be used dry. It's important to check the specific instructions provided by the manufacturer for the recommended usage and maintenance of your particular whetstone.