The Fine Arts Laboratory and Scientific Services at the Canadian Conservation Institute have initiated a project to investigate alternatives available for the lining of paintings. The goal of the project is the identification of a range of suitable lining support systems, with defined physical and mechanical properties, which will minimize stress development in a painting. The project is divided into 4 stages: Mechanical Testing of Model Paintings; Peel Testing of Lining Adhesives; Testing of the Mechanical Properties of Lining Supports; and Testing of Lined-Model Paintings. The first phase of the project is nearing completion. The prepared samples include combinations of linen canvas, glue size, oil and acrylic grounds, and oil paint. The samples are mounted in uni-axial restraining devices which permit measurement of stress relaxation over the long term, stress with applied strain, and stress as a function of Relative Humidity (RH). Measurements also included weight change, and freehanging dimensional change in response to change in RH. Notable results to date are the following: In samples prepared as Model Paintings, there is a dramatic increase in stress at low RH, and a loss in stress at moderately high RH. Stress relaxation may follow a simple equation that might permit prediction of eventual stress in a sample from values obtained in the first five minutes after strain is applied. A wide variation in the speed of response of the different sample types was noted. Following a change in ambient RH, the maximum response of the samples, in weight and dimension, occurred within approximately 1 - 3 1/2 hours. -- AATA