Accounts filed at Companies House show turnover dipped 9% from £14.84 million to £13.5m during 2012. UK income fell from almost £14.6m to less than £13.4m while exports dropped from £269,000 to £144,000.
The previous year's pre-tax profit of £712,000 reversed into a loss of £69,000 according to the financial statement. Operating costs fell from £14.16m to £13.59m mainly due to a smaller charge for raw materials and consumables.
The directors warned prospects were uncertain and said: "With tightening markets and an unsure outlook, the directors feel it is difficult to forecast the result for the year ahead."
However they pointed to the company's balance sheet, which shows net assets of £5.2m, saying its financial positions remains strong.
Charles Tennant, which has sites in Blantyre, South Lanarkshire, and Edinburgh, supplies chemicals, acids and solvents to customers including BP Chemicals, Ineos, Gem Plastics and Esseco.
According to the accounts, average staff numbers increased by one to 37 with overall employee costs rising from £1.25m to £1.3m. Directors' emoluments and pension payments were steady at £112,000. An ordinary dividend of £600,000 was proposed for the year, up from £132,000 for 2011.
The company, part of London-based Tennant Consolidated, can trace its origins to the 18th century when founder Charles Tennant invented bleaching powder.
The innovation by the apprentice weaver helped to revolutionise the linen trade by reducing the time, effort and cost in bleaching cloth before it was dyed.
After he was granted a patent, Tennant went on to build a huge chemical plant in Glasgow.