Quite recently cellulose ethers have been introduced into the conservation field as an adhesive agent. Cellulose ethers are available in a wide range of products. Their properties are related not only to the nature of the substituent but also to the degree of polymerization (DP) and the degree of substitution (DS). Thus, the number of OH groups that are bound to C1 and C4 or to C2, C3 and C6 carbon atoms of the cellulose ether molecule affect their properties. Paper traction resistance is increased by using cellulose ethers as an adhesive to paste Tenguyo paper, a paper with a low density of fibres usually used by restorers. This increase is directly related to the molecular structure of the cellulose ethers. Therefore, the nature of substituents, the DP and the DS of cellulose ethers have to be taken into account in conservation practice. DP equals the number of anhydroglucose units in the chain and DS equals the number of hydroxyl groups replaced by the substituent in every anhydroglucose unit in the chain. As this information is not usually provided by suppliers, viscosity measurements are proposed as a means of predicting the behaviour of different products in relation to the conservation of paper artefacts, or to any other field where cellulose ethers solutions are used.