Development of durable natural colorants for wooden surfaces with plant extracts and liquid glass mixture and determination of the color change performance

The aim of this study is to develop new types of natural colorants that are resistant to external conditions; natural aging, cold-check and salt spray tests with a mixture of plant extracts and liquid glass. Wood is a natural and basic building material, which used extensively in indoor and outdoor environments where people and living things live. Besides many advantages, wood has some disadvantages such as degradation by biotic and abiotic factors, deformation, discoloration and so on. To solving these problems different wood preservatives and colorants were developed to protect wood material. It is proven by scientific studies, colorants and preservatives that are used for wood protection and esthetic are containing substances have some side effects on human and environmental health, so, there is a demand to "green" products that are environmentally-friendly (Leitner, 2012). In recent years, colorants, water-based varnishes, boron compounds and similar natural wood preservatives have been developed against biotic and abiotic pests that harm wood material, which are harmless or less harmful to the environment and human health. However, there are scientific studies showing that these natural products do not partially or completely fulfill the functions expected from them, especially when they are used outdoors, they undergo degradation such as washing, color change, burning and decay. (Kartal ve ark 2006; Baysal, 2005). Therefore, increasing the resistance of natural wood colorants, especially to be used outdoors, against biotic and abiotic pests has emerged as a new problem to be solved. For solving the problem, this study will be an original study in the literature on protection degree of liquid glass+natural dye coated on wood against to hazardous factors. The theory of this study is, liquid glass can be used as a coating material for its high protective capacity, and with a mixing of natural dye staff, and it can be developed durable natural and protective wood stains. Within the study, colorant extracts obtained from walnut shell (Juglans regia), licorice (Glycyrrhiza glabra L.) and pomegranate skin (Punica garnatum L.) were mordanted with iron sulfate (Fe2(SO4)37.H2O), aluminum sulfate (Al2(SO4)318.H2O), and vinegar (CH3COOH). The prepared dyes were mixed with liquid glass and applied with dipping method to siberian pine (Pinus sibirica), scotch pine (Pinus sylvestris L.), red pine (Pinus buria), iroko (Milica excelsa) and spruce (Picea orientalis) test samples. In addition to the developed plant extract-liquid glass mixture and for comparison, a commercial wood colorant used in the industrial environment is also included. Coated wood samples were tested to evaluate the protection degree of liquid glass+natural stains against to discoloration by natural aging, salt spray and cold check tests. According to the natural aging test data, liquid glass has different results according to various wood species and mixtures, but gave significant and positive results when compared with synthetic dye in the color change caused by natural aging effect. It was determined that liquid glass mixture of liquorice dye with vinegar mordant provides significant resistance to natural aging. According to the cold check test data, the effect of the liquid glass was insignificant in walnut skin and licorice dyes. Pomegranate skin dye mixture has reduced the color change compared to the mixture without liquid mixture. According to the salt spray test results; It can be said that the mixture of licorice and liquid glass with vinegar mordant provides more resistance than synthetic dye and can be developed as an alternative to synthetic dyes.