When first taken from the animal and emptied, natural casings typically have five layers. From lumen to exterior
  1. mucosa, composed of epithelial, glandular and vascular components
  2. submucosa composed of connective tissues that strengthen the gut wall
  3. circular layer of smooth muscle cells
  4. longitudinal layer of smooth muscle cells
  5. irregular layer of visceral fat covering the outside.

The fat is removed manually and by machine brushing. The intestinal contents are squeezed out and washed away in a process called stripping. Finally, the layers of muscle and mucosa are removed as the intestine passes between a pair of rollers in a process called sliming. This leaves the strong connective tissues of the submucosa as the sausage casing.

The commercial properties of casings originate from the high collagen content of the submucosa, together with smaller amounts of elastin.

Casings often are turned inside-out to faciliate processing.

Clean casings are preserved with dry sodium chloride prior to sale.

With approximate metric lengths given in parentheses, the commonly used beef casings are

Beef casing are tough and strong, and are usually removed before consumption of the product - like skinning a slice of salami.

The commonly used hog casings are

  1. rounds or small casings from the small intestine (18 m)
  2. cap from the caecum (0.4 m)
  3. middles from the middle part of the large intestine (1 m)
  4. bung from the terminal end of the large intestine (1 m)

Being intermediate in tenderness, beef casings either may be eaten or removed before consumption of the product.

The small intestine from sheep provides 27 m of tender casing that gives natural-casing wieners their "snap".