A woman's sack back and petticoat, of white satin, figured with a serpentine vertical ribbon with flowers and separate floral sprigs, and brocaded in flowers with silk in shades of pink and green. The sack back is open at the front, with elbow-length sleeves. The bodice and sleeves are lined with linen. The sack back is made of 4 widths of silk with a partial width and triangular gore of silk on each side of the fronts. The back has two, double box pleats stitched at the neck line. The waist seam extends from the front opening of the skirts to the side back seam of the bodice. The skirt fronts are pleated at the bodice side back seam, on either side of the pocket openings. The skirts and skirt fronts are faced with white silk taffeta. The skirts are decorated with a narrow band of silk gathered into puffs and edged with a fringe of white silk twist and chenille with pink and green floss knots, arranged in straight line along the front edge. Parallel to these are a broader ruching gathered in the centre and edged with the fringe. Two silk cord loops are sewn to the inside of the gown skirts on either side of the back, however there are no corresponding buttons or evidence of such on the inside or outside of the skirts.
The petticoat is made of 5 widths of silk, with a box pleat at the centre front and flat pleats at the sides and back. The waist is bound with linen tape extending to ties that fasten at either side at the pocket openings. The hem is faced with a band of linen. The petticoat is decorated with a band of ruching, gathered in the centre and edged with the silk fringe, in a straight line above the hem. Above is a deep flounce of gathered silk, edged at the bottom with the silk fringe. Above the flounce is a narrow band of silk gathered into puffs and edged with the silk fringe.
The sack back and petticoat were probably made in the early 1770s. Towards the end of the decade the sack back was altered to update the style. The robings were unpicked and opened and the bodice fronts relined. The ruching around the neckline was added. The sleeves may originally had two ruffles, edged with the silk fringe, which were converted to ruched cuffs.