Ointment bases are preparations with very specific properties: The pharmaceutical ointments constitute single-phase, semi-solid and spreadable emulsions with incorporated active substances. The active substances are added in accordance with a specific recipe. In the emulsion, active substances are dissolved, dispersed or suspended. There are different kinds of ointments which contain different bases. In the case of a so-called hydrophobic ointment, a very small quantity of water is folded in by means of mechanical dispersing. Water-repellant ointments are very greasy, are hydrophobic and cannot be washed off with water. The basis of a hydrophilic ointment can be mixed with water; this type of ointment is single-phase. Although the hydrophilic ointments are greasy, they do not leave oily residues, are also shiny and can be washed off with water. Another type of ointment is the water-absorbing ointment, which can absorb enormous amounts of water during the building of an emulsion. An emulsion constitutes a finely distributed, stable mixture of two normally immiscible liquids, whereby one phase of the emulsion is distributed in the form of fine droplets in the other medium. A distinction is made between water-in-oil (W/O) and oil-in-water emulsions (O/W).
Homogenising mixers lend themselves to the production of pharmaceutical ointments. Modern machines can rapidly disperse solids in liquids, hydrate expanding agents and stabilisers, dissolve agglomerates, reduce particles and create a fine, stable emulsion or suspension. These homogenising mixers greatly reduce the mixing time and significantly improve the stability and consistency of the products.