…the same stuff that masons use to clean bricks.

Luckily, our stomachs are lined by a thick layer of mucus to protect us from the acid and the enzyme pepsin that it produces. The mixing motion of the stomach, along with the acid and the breakdown of protein by the pepsin, turns the bolus (the food you just swallowed) into a liquid substance called chyme, which in turn is then slowly released into the small intestine. For a full meal, this process takes approximately two to three hours.

Very few substances are absorbed into the bloodstream directly from the stomach, and notably, these are the very substances that can cause stomach irritation: alcohol, aspirin, and non-steroidal anti-inflammatory drugs (NSAIDs). Otherwise all other nutrients are absorbed in your blood stream via the small and large intestines.

Source: https://www.verywell.com/digestive-system-facts-1944708