Compositions suitable for the production of films, foils, dopes, varnishes, plastics, and the like, comprise a cellulose derivative and a formal of an hydroxy carboxylic acid. Suitable formals are those obtained by condensing formaldehyde with a -hydroxy iso-butyric acid a -hydroxy normal butyric acid, lactic acid, and glycollic acid. The formals may be employed in conjunction with other solvents or diluents, a number of which are specified. The Specification as open to inspection under Sect. 91 relates also to processes for condensing hydroxy carboxylic acids with aldehydes or ketones, and specifies formaldehyde, trioxymethylene, para-formaldehyde, acetaldehyde, benzaldehyde, acetone, and cyclohexanone as suitable aldehydes or ketones. The condensation products may be used as solvents or softeners for cellulose esters, natural or artificial resins, and as solvents for dyestuffs. Of particular importance is their application in the manufacture of artificial silk, films, sheets, dopes, varnishes, plastics, and the like, containing cellulose esters. For example, they may be employed in wet spinning processes, in the coagulating bath as is described in Specifications 179,234, [Class 2 (ii)], 340,324, and 340,325, and in subsequent treatment baths as in Specification 340,437. The condensation products may also be employed in the treatment of artificial filaments, films, fabrics, and the like, to reduce the tendency to slip, split, or ladder, as in Specification 280,990, [Class 42 (i)]; to improve the pliability by shrinking, as described in Specification 389,823; and to improve tenacity by stretching according to the processes of Specifications 277,089, 323,790, [both in Class 2 (ii)], 370,430, and 371,461. They may also be used in the preparation of sizes for textiles. Filaments, films, fabrics, and the like may be treated with the condensation products to facilitate absorption by the materials of substances adapted to dye, print, load, mordant, and delustre the materials. A further application is to relustre, uniformly or locally, fabrics which have been delustred by the action of moist steam or of hot aqueous liquids according to the process of Specification 259,265, [Class 2 (ii)]. The following examples are included: (1) Cellulose acetate is worked up with a mixture of tricresyl phosphate, mono-methylated isomeric xylene sulphonamides, benzene, alcohol, and the condensation product of acetaldehyde and glycollic acid. (2) A lacquer comprises nitrocellulose, diphenylol propane formaldehyde resin, the condensation product from acetaldehyde and a -hydroxybutyric acid, triphenyl phosphate, acetone, butyl acetate, and alcohol. (3) A lacquer comprises cellulose acetate, diphenylol propane formaldehyde resin, dibutyl tartrate, tricresyl phosphate, acetone, dioxane, condensation product from formaldehyde and a -hydroxy iso-butyric acid. (4) A coating composition contains polymerized vinyl acetate, diphenylol propane formaldehyde resin, tricresyl phosphate, condensation product from benzaldehyde and a -hydroxy iso-butyric acid, alcohol, and acetone. (5) A solution of cellulose acetate in acetone is extruded into an aqueous bath comprising diacetone alcohol and the condensation product of formaldehyde with a -hydroxy iso-butyric acid. The spinning solution may also contain a small amount of the condensation product. (6) A solution of cellulose acetate in acetone and the condensation product from formaldehyde and glycollic acid is spun into an evaporative atmosphere. (7) A hank of cellulose acetate yarn is soaked in an alcoholic or aqueous alcoholic solution of the product from formaldehyde and a -hydroxy iso-butyric acid, and stretched. Specification 380,504 also is referred to. This subject-matter does not appear in the Specification as accepted.ALSO:Coating compositions comprise a cellulose derivative and a formal of an hydroxy carboxylic acid. Suitable formals are those obtained by condensing formaldehyde with a -hydroxy iso-butyric acid, a -hydroxy normal butyric acid, lactic acid, and glycollic acid. The formals may be employed in conjunction with other solvents and/or diluents, a number of which are specified. The Specification as open to inspection under Sect. 91, relates also to processes for condensing hydroxy carboxylic acids with aldehydes or ketones, and specifies formaldehyde, trioxymethylene, paraformaldehyde, acetaldehyde, benzaldehyde, acetone, and cyclohexanone as suitable aldehydes or ketones. The condensation products may be used as solvents for cellulose derivatives and/or natural or artificial resins. Examples are given of coating compositions containing nitrocellulose and the condensation product of acetaldehyde and isobutyric acid; cellulose acetate and the condensation product from formaldehyde with a -hydroxy butyric acid; and polymerized vinyl acetate and the condensation product of benzaldehyde and a -hydroxy butyric acid. This subject-matter does not appear in the Specification as accepted.ALSO:Compositions comprise a cellulose derivative and a formal of an hydroxy carboxylic acid. Suitable formals are those obtained by condensing formaldehyde with a -hydroxy iso-butyric acid, a -hydroxy normal butyric acid lactic acid, and glycollic acid. The formals may be employed in conjunction with other solvents and/or diluents, a number of which are specified. The Specification as open to inspection under Sect. 91 relates also to processes for condensing hydroxy carboxylic acids with aldehydes or ketones, and specifies formaldehyde, trioxymethylene, para-formaldehyde, acetaldehyde, benzaldehyde, acetone, and cyclohexanone as suitable aldehydes or ketones. The products may be used as solvents for cellulose derivatives and/or natural or artificial resins. An example is given of a composition obtained by working up cellulose acetate with a mixture of tricresyl phosphate, mono-methylated isomeric xylene sulphonamides, benzene, alcohol and the condensation product of acetaldehyde with glycollic acid. The condensation products may also be employed in the preparation of sizes for textiles. This subject-matter does not appear in the Specification as accepted.