Extraction of Anthocyanin Dye from Staghorn Sumac Fruit in Various Solvents and Use for Pigment Printing

Abstract

This study investigates the potential of the dye extracted from the fruits of the alien invasive plant staghorn sumac (lat. Rhus typhina) as a sustainable and environmentally friendly colorant. By using a range of solvents, including distilled water, methanol, ethanol, propanol, acetonitrile, acetone, and dichloromethane, this study aims to determine the optimum solvent for the extraction of anthocyanin dyes from the fruit of staghorn sumac for the formulation of printing inks and for screen printing on paper and cotton fabric. The colors of the prints made with different dye extracts varied between more or less intense brownish-yellow hues, with the exception of the dye extracts in methanol and ethanol, which gave more brownish-orange hues. All prints showed excellent resistance to rubbing on cotton fabrics as well as to wet ironing. The light fastness of prints made with inks containing dyes extracted from all organic solvents was very good. Good wash fastness of prints on cotton fabrics was only achieved with inks made with dyes extracted in propanol and dichloromethane. The ink made from the dye extracted in propanol proved to be the best choice for printing on cotton fabric due to its uniform, intense, and resilient prints, while the inks made from the dyes extracted in distilled water and ethanol were also a good choice for printing on paper.

1. Introduction

Rhus typhina L., also called Rhus hirta L., commonly known as staghorn sumac, is a popular ornamental shrub or small tree 5–10 m tall, native to eastern North America. It has large, pinnately compound leaves with separate leaflets and red fruits, which are conical clusters of small, compact reddish drupes 3 to 5 mm in size that ripen from June to September [1]. In Europe, the species is known as an invasive plant, as it grows excessively in colonies under different environmental conditions. Its excessive spread, which aggressively displaces native plants, is becoming an ecological problem and presents us with the challenge of how we can use this plant in as many beneficial ways as possible.

The usefulness of staghorn sumac fruit for nutritional and medicinal purposes is already well known. The fruit has been used by indigenous people of North America since ancient times to create a drink called sumacade, or Indian lemonade, and to treat the symptoms of diabetes. The fruits have been shown to have antioxidant, antimicrobial, antifungal, anticancer, and anti-inflammatory effects, and they can be used in the formulation of pharmaceutical and cosmetic products [1,2,3,4,5,6]. The aqueous extracts of staghorn sumac fruit powder have also been shown to be healthy and useful ingredients in wheat bread formulation, prolonging the shelf life of bread [7].

The chemical composition of staghorn sumac fruit has been studied in detail for its various beneficial compounds and found to contain various polyphenolic compounds, including phenolic acids and flavonoids such as anthocyanins and pyranoanthocyanins [1,2,3,4,5,6]. The most important polyphenolic compounds are gallic acid, which is a powerful antioxidant and has a high anti-inflammatory potential, and anthocyanins, which are responsible for the red coloration. The fruit contains mostly anthocyanins, with peonidin, cyanidin, and delphinidin as the anthocyanidins [1,2,3,4,5,6]. The anthocyanin composition of staghorn sumac differs from that of common fruits and vegetables. Staghorn sumac fruit has a unique flavonoid composition, especially two pyranoanthocyanins such as sumadin A and sumadin B [4].

In addition to the use of staghorn sumac as food and medicine, attempts have been made to utilize the plant in other ways. The dye from the fruits of staghorn sumac has been used to produce reddish-colored hydrophobic coatings for wood [8]. It has also been shown that the extract from staghorn sumac fruit can be used as a natural pH indicator for determining the acidity and alkalinity of solutions [9]. Furthermore, it has been used in the production of color-sensitive solar cells, but with a lower solar energy conversion efficiency than the synthetic dye currently used [10]. In all these studies, the red dye was obtained by extracting the fruits in ethanol with hydrochloric acid, filtering, and evaporating the solvent.

Although it is known that various parts of staghorn sumac, such as the fruits, leaves, and bark, can be used to obtain natural dyes for textile dyeing or printing, there is little scientific research in this area.

The following studies were carried out in the field of dyeing and modification of textile materials. The fruits of staghorn sumac extracted in distilled water and methanol were used to dye cationic pretreated cotton fabric. The dyeing with aqueous extract resulted in a darker and more reddish color compared to the dyeing with the extract in methanol [11]. The use of an aqueous extract of sumac bark was investigated for dyeing pre-mordanted wool fabric with various metal salts, which gave a reddish-brown color and good UV-protective properties to the wool fabrics [12]. The extracts of leaves and drupes of staghorn sumac were used as reducing agents for ZnO formation directly on cotton, designing UV-protective and hydrophilic or hydrophobic cotton fabrics [13].

In the field of the production of printing inks and textile printing, only one study was found that investigated how insoluble pigments can be produced in brown, green, or black colors by precipitation from alkaline aqueous extracts of fruits and leaves of staghorn sumac with various metal salts such as aluminum, copper, and iron sulfates. The least amount of pigments was obtained from the fruits of staghorn sumac, as the extract is very acidic, while more pigments were obtained from the leaves of staghorn sumac. These pigments were not successfully used for printing on cotton fabric, resulting in uneven prints [14].

The use of natural dyes in the textile industry represents an important step towards environmental sustainability and consumer demand for more environmentally friendly products, which is why further studies on the use of natural dyes from staghorn sumac need to be carried out.

Our study demonstrates the use of soluble dye extracts from staghorn sumac fruit for screen printing on cotton fabric and paper. Normally, printing with natural dyes is only carried out on fabrics, but in our investigation, paper with a higher grammage, which is made from primary cellulose fibers, has also proven to be a potential substrate. The aim of our research was also to determine the influence of the various solvents of different polarities used for extraction on the color of the extract, on the color and formulation of the screen printing inks, and on the color and quality of the prints by visual and spectrophotometric evaluations and by testing the fastness properties of the prints.

For the formulation of the printing inks, the printing paste with an acrylic binder and an acrylic thickener for pigment printing was used, as it has already proven itself in the formulation of screen printing inks with extracts of natural dyes from other invasive plants for printing on paper and fabric [15,16]. The printing inks made from aqueous dye extract were formulated from two different pigment printing pastes for comparison: the printing paste, which has to be produced from individual acrylic components, and the commercially available, ready-to-use pigment printing paste, in which all the components are already mixed, thus simplifying the process of ink production.

The study also tested the process for the preparation of insoluble pigments using the aqueous extract, the participation of soda ash and copper sulfate, as shown in the previous study [14], and the possible use of precipitated pigments for application in the pigment printing paste.

The results obtained contribute to a better selection of solvents for the extraction of dye from staghorn sumac fruits for optimal prints and fastness properties on cotton fabric and paper.

2. Materials and Methods

2.1. Materials

2.1.1. Staghorn Sumac and Chemicals for Extraction

The fruits of the staghorn sumac were collected in Slovenia in August and October 2020 and stored in the freezer until further processing.

The extraction of the dye from the fruits of the staghorn sumac was carried out with seven different solvents, including: methanol (Carlo Erba Reagents, Emmendingen, Germany), ethanol 99.8% (Riedel-de Haën, Buchs SG, Switzerland), 1-propanol (Riedel-de Haën, Buchs SG, Switzerland), acetone (Riedel-de Haën, Buchs SG, Switzerland), acetonitrile (Riedel-de Haën, Buchs SG, Switzerland), dichloromethane (Riedel-de Haën, Buchs SG, Switzerland), and distilled water with a pH value of 5.5.

Acetic acid 99.8% (Sigma Aldrich, St. Louis, MO, USA) was used for extraction in ethanol. Aluminum potassium sulfate dodecahydrate (Carlo Erba Reagents, Emmendingen, Germany), sodium carbonate anhydrous 99.8% (Sigma Aldrich, St. Louis, MO, USA), and copper sulfate pentahydrate (Honeywell Fluka, Seelze, Germany) were used for the extraction in distilled water.

2.1.2. Pigment Printing Pastes

Two printing pastes for pigment printing on textiles were used to formulate the screen printing inks. A printing paste with a pH value of 7.43 was prepared by mixing the individual ingredients: 150 g of Binder SE conc (Achitex Minerva S.p.A., Vaiano, Cremasco, Italy), a self-crosslinking acrylic copolymer binder; 40 g of Clear MCS (Achitex Minerva S.p.A., Vaiano, Cremasco, Italy), an acrylic thickener; and up to 1000 g of distilled water. The printing paste was used to produce screen printing inks with all dye extracts.

The second printing paste was a commercially available ready-to-use water-based pigment printing paste, Elastil Transparent FGI (Achitex Minerva S.p.A., Vaiano, Cremasco, Italy), with a pH value of 8.06, which was used only for the preparation of the screen printing ink with the dye extract in distilled water.

2.1.3. Printing Substrates

The following materials were used for printing: white paper made from virgin cellulose fibers with the trade name IQ premium (manufactured by Mondi Group Ltd., Vienna, Austria) with a grammage of 200 g/m², and cotton fabric, woven in linen, chemically bleached and mercerized (manufactured by Tekstina Ltd., Ajdovščina, Slovenia) with a surface mass of 122.73 g/m².

2.2. Methods

2.2.1. Dye Extraction

For the extraction, the red fruit drupes were separated from the stem and crushed. A total of 100 g of smaller particles of the drupes were soaked in the following amounts of each solvent: 700 mL methanol, 750 mL ethanol, 800 mL propanol, 700 mL acetonitrile, 700 mL acetone, 1200 mL dichloromethane, and 2000 mL distilled water. Acetic acid was added to the extracted ethanol solution at a concentration of 20 mL/L to see the possible influence on the color of the extract.

The extractions in the solvents were carried out for one week at room temperature. After one week, the fruits were removed from all solvents by filtration. The colored solutions in the different solvents were left open for two weeks to allow the solvent to evaporate in the fume hood, and the concentrated dye extracts were obtained.

A schematic representation of the process of extracting dye from staghorn sumac fruits can be seen in Figure 1.

Only the extraction in distilled water was carried out differently, with the addition of aluminum potassium sulfate during boiling in the following procedure. The 100 g of fruit drupes in 1500 mL of water were boiled for 20 min, and then 50.04 g of dissolved potassium alum per 500 mL of distilled water was added, boiled for a further 25 min, and then left to cool overnight. The solution was then filtered to remove the drupes. A total of 250 mL of dye solution was obtained and allowed to evaporate at room temperature.

A further 700 mL of water was added to the remainder of the fruit drupes and boiled for 11 min, allowed to stand at room temperature for a week, and then filtered to obtain a further 220 mL of dye solution. To 100 mL of this dye solution in water, 2 g of sodium carbonate and then 2 g of copper sulfate were added. It was allowed to evaporate, and after two weeks, the pigment was precipitated.

2.2.2. Preparation of Printing Inks

Since different amounts of the concentrated extract were obtained in different solvents, the amount of dye extract added to the previously mixed printing paste with a pH value of 7.43 was different. The printing inks were prepared in the following concentrations: 1.5 g of the dye extract prepared in methanol, ethanol, propanol, and acetone was added to 50 g of printing paste; 0.95 g of the dye extract in acetonitrile was added to 32 g of printing paste; and 0.39 g of the dye extract in dichloromethane was added to 30 g of printing paste.

Two different printing inks were produced with aqueous dye extracts: 1.5 g of dye extract in distilled water was added to 50 g of the prepared printing paste with a pH value of 7.43 and 1.5 g of dye extract was also added to 50 g of the commercially already-prepared Elastil Transparent FGI paste with a pH value of 8.06.

A total of 1.5 g of precipitated pigment, prepared from the dye extract in distilled water with additions of sodium carbonate and copper sulfate, was also added to 50 g of printing paste with a pH value of 7.43.

In this way, nine different printing inks were produced with dye extracts in various solvents for screen printing.

2.2.3. Printing

The printing inks were applied to the substrates using a semi-automatic SD 05 screen printing machine (RokuPrint Ltd., Darmstadt, Germany) equipped with a flat polyester mesh screen with a density of 77 threads/cm and a thread diameter of 55 μm. The printing process was carried out in three strokes with a squeegee. After application, the prints were dried overnight at room temperature before being cured at a temperature of 150 °C for 5 min.

2.2.4. Color Measurements

Color measurements of the prints were taken one week after printing using the Eye-One i1 Pro spectrophotometer (X-Rite, Grand Rapids, MI, USA) with 45/0 plane geometry, illuminant D65, 10° standard observer, and a 4.5 mm diameter aperture. CIELAB color coordinates, which include L* (lightness), a* (red-green value), and b* (yellow-blue value), were measured, and the average of three measurements was taken for each sample. In addition, hue (h_ab) and chroma (C*_ab) were calculated.

2.2.5. Fastness Tests

The durability of the ink layer on printed papers was evaluated by an abrasion test according to ASTM D 5264-98 [17]. This evaluation was performed using the RT-01 digital ink rub tester (Labthink Ltd., Neu-Isenburg, Germany), applying a rubbing pressure of 2 kg and a frequency of 1.8 s⁻¹ over 500 cycles. The degree of ink transfer from the printed surfaces to a standard white paper, which served as a receptor, and the condition of the printed surfaces after rubbing were visually assessed.

The resistance of the printed fabrics to dry and wet rubbing was determined using an electronic Crocmeter rub tester (SDL Atlas, Rock Hill, SC, USA) according to the protocol described in ISO 105-X12: 2016 [18]. In addition, the stability of fabric prints during wet ironing was tested in accordance with ISO 105-X11: 1994 [19]. The resistance of the prints to domestic and commercial laundering was tested according to ISO 105-C06: 2012—Test A1S at 40 °C for 30 min in the standard Launder-O-meter washing machine (SDL Atlas, Rock Hill, SC, USA) [20]. After the fastness tests, the degree of color change in the prints and the degree of staining of the adjacent white fabric were visually assessed using gray scales according to ISO 105-A02 [21] and ISO 105-A03 [22] with ratings from 1 to 5, where 5 means excellent fastness.

The light fastness of prints on fabrics and papers was tested in accordance with ISO 105-B02: 2014 using a xenon arc lamp in the Xenotest Alpha device (Atlas, Rancho Cucamonga, CA, USA) under controlled conditions of 35 °C, 35% relative humidity, and a 72-h exposure time [23]. At the same time, a comparison was made with the blue standard reference scale. After exposure, the degree of fading of the prints was visually assessed using blue wool standards graded from 1 to 8, with 8 indicating excellent light fastness.

3. Results and Discussion

3.1. Extracts, Printing Inks, and Prints

The different solvents used for the extraction of red-colored staghorn sumac drupes affected the color of the extract, which ranged from yellow to brownish-red (see

Table 1. Comparison of colors of extracts, printing inks, and prints.

Color of Staghorn Sumac Fruit	Dye Extract	Color of Solution after Filtering	Color of Extract after Solvent Evaporation	Concentration of Printing Ink	Color of Printing Ink	Color of Print on
						Paper	Cotton Fabric
	in distilled water			1.5 g dye extract /50 g printing paste
	in distilled water			1.5 g dye extract /50 g Elastil T. printing paste
	in methanol			1.5 g dye extract /50 g printing paste
	in ethanol			1.5 g dye extract /50 g printing paste
	in propanol			1.5 g dye extract /50 g printing paste
	in acetonitrile			1.48 g dye extract /50 g printing paste
	in acetone			1.5 g dye extract /50 g printing paste
	in dichloro- methane			0.67 g dye extract /50 g printing paste
	in water with soda in copper sulfate			3 g precipitated pigment /50 g printing paste		-	-

), and the amount of dye extracted. Table 1 lists the extracts in solvents from top to bottom in descending order of solvent polarity and shows the comparison between the colors of the starting solutions of different solvents, the extracts, the inks, and the prints. The photographs of the prints shown in Table 1 do not show exactly the correct colors of the prints that were seen. The spectrophotometric measurements of the colors of the prints on paper and cotton fabric have been summarized in

Table 2. Color values of prints on paper and cotton fabric.

Dye Extract	L*	a*	b*	C*ab	hab [°]
Paper
distilled water	91.63	0.59	−3.55	3.60	88.42
distilled water/Elastil T. paste	90.57	−0.04	−1.13	1.13	87.97
methanol	88.06	1.38	4.88	5.07	74.21
ethanol	91.59	1.51	−4.18	4.44	70.14
propanol	92.11	0.40	−3.27	3.29	78.67
acetonitrile	93.11	1.42	−7.09	7.23	78.67
acetone	90.05	−0.21	2.92	2.93	85.89
dichloromethane	92.33	0.87	−5.18	5.25	80.47
Cotton Fabric
distilled water	87.43	−1.07	9.42	9.48	89.26
distilled water/Elastil T. paste	88.14	−1.82	8.77	8.96	78.28
methanol	85.03	0.98	14.42	14.45	79.46
ethanol	88.15	0.46	10.43	10.44	87.47
propanol	90.02	−2.06	11.39	11.57	79.75
acetonitrile	90.33	−0.71	5.28	5.33	82.34
acetone	86.65	−1.43	15.95	16.01	84.88
dichloromethane	90.03	−1.39	7.47	7.60	79.46

.

It is known that anthocyanins give the fruits of the staghorn sumac a red color [9]. Methanol, ethanol, propanol, acetone, and water were effective solvents for extracting the anthocyanin dye. From the 700–800 mL of organic solvents used for 100 g of fruit drupes, about 1.5 g of concentrated dye extract was obtained. It is known that anthocyanins are more soluble in acidic solvents, which is why acidified solvents are generally used for the extraction of anthocyanins from plants [24]. However, when the staghorn sumac fruit was extracted in polar solvents such as alcohols, the acidic compounds were also extracted from the fruit together with the anthocyanins, so that the extracts were already acidic. In our experiment, the solution extracted in ethanol was acidified with acetic acid, but neither the intensity nor the hue of the brownish-red ethanol extract changed. When extracting with other solvents, the acid was not added additionally, also because the pigment printing paste is pH-sensitive and develops its optimum viscosity for screen printing at a pH value of 7.4–8, and an extract that is too acidic can reduce the viscosity.

The smallest proportions of the anthocyanin dye were extracted by acetonitrile, which yielded less than 1 g of dye, and particularly by nonpolar dichloromethane, which, due to its rapid evaporation, was used in even larger quantities (1200 mL) and yielded the smallest amount of dye, less than 0.4 g. This shows that the polar anthocyanin dyes are not readily soluble in the non-polar dichloromethane and are also less soluble in the polar aprotic solvent acetonitrile, which is why the printing inks were produced with these extracts in lower concentrations than with other extracts.

Extracts of staghorn sumac fruits in polar solvents such as distilled water, methanol, and ethanol were brownish-red (Table 1). After addition to the printing paste with a pH of 7.43, the extract in methanol colored the printing paste reddish-pink, the extract in ethanol orange-pink, and the color was lighter than that of the extract in methanol. The resulting prints, which had a spectrophotometrically measured orange-yellow color hue on paper and yellow on cotton (h_ab in Table 2), were visually brownish-orange (Table 1). The prints obtained with the methanol extract were darker and more intense than with ethanol (Table 2), but with the ethanol extract, the prints were visually more uniform on both substrates than with methanol, where a uniform print was obtained only on paper.

The most significant color change occurred when brownish-red extract in distilled water with a pH of 5.5 was added to the printing paste with a pH of 7.43, prepared from individual components; because the pH value increased, the color became light brown (Table 1), resulting in light brownish-yellow uniform prints with a spectrophotometrically measured yellow hue (Table 2). The prints were slightly greener when Elastil Transparent printing paste with a pH value of 8.06 was used for the formulation of printing inks. The ready-to-use printing paste Elastil Transparent was not suitable for the formulation of the printing ink with the dye aqueous extract, as it caused uneven prints and also a sticky feel compared to the printing paste produced by mixing individual components, with which uniform prints were achieved.

A brownish-green color developed when sodium carbonate and copper sulfate were added to the brownish-red aqueous extract, from which the brownish-green dusty pigment was precipitated (Table 1). The precipitation method was used because the only study on printing with the colorants of the same fruit used this type of extraction [14], and we wanted to compare the use of insoluble pigment with the soluble dye extracts. When this pigment was added to the printing paste, it colored the paste turquoise blue, but the viscosity of the ink decreased so much that the ink could not be used for screen printing. The reduced viscosity of the ink was caused by copper ions reacting with the anionic carboxylate groups of the thickener, and since the polymer chains of the thickener were no longer electrostatically repelled, the thickener lost its corresponding swelling and thus its viscosity. The use of copper-containing pigments in prints on textiles or paper is not advisable from a health and ecological point of view, even if the content is low, and it reduces the environmentally friendly properties of the natural dye.

Staghorn sumac fruits extracted in propanol and acetone gave a brownish-yellow color to the solution, which was slightly more orange in propanol, from which brownish-yellow extracts were obtained. In the printing paste, the extract in propanol gave a lighter yellow color and the extract in acetone a light brown color, and with both extracts, the brownish-yellow prints (Table 1) were obtained with a spectrophotometrically measured yellow hue (Table 2). The uniform prints were obtained only with the propanol extract.

Staghorn sumac fruits in acetonitrile and dichloromethane gave a greenish-yellow color to the solution. The yellowish-brown extract of acetonitrile gave light yellow ink, which yielded light brownish-yellow, uneven prints (Table 1) with a spectrophotometrically measured yellow hue (Table 2). The greenish-yellow extract in dichloromethane gave greenish-yellow ink and very light brown-yellow prints as in acetonitrile, but more uniform (Table 1) with a spectrophotometrically measured yellow hue (Table 2).

The prints on cotton fabric were slightly darker and more saturated (with a higher chroma value C*_ab) compared to the prints on paper (Table 2), as more ink can be absorbed into the textile fibers than into paper, and the prints on fabric have a high value of b* in the yellow range.

The most intense and darkest prints on both substrates were obtained with inks whose dye was extracted in methanol, acetone, propanol, and ethanol. The lighter and less intense prints were produced with the dye extracted with acetonitrile and dichloromethane; however, this was to be expected due to the lower amounts of dye extracted in these solvents, as a lower concentration of dye extract was added to the ink. More uniform prints were achieved with inks made from dyes extracted in ethanol, propanol, dichloromethane, and distilled water with the printing paste prepared with individual ingredients, as well as on paper with the ink made from the extract in methanol. In assessing the effectiveness of extraction solvents, it should be noted that dichloromethane, methanol, and acetonitrile are particularly hazardous to health, toxic, or carcinogenic [25] and should be avoided.

The color of the anthocyanins depends strongly on the pH value of the solution, which leads to structure changes in the anthocyanidin chromophore, which are shown in Figure 2 [26,27].

At a pH value below 3, the anthocyanins are predominantly present in the form of flavylium cations, at a pH value of 4–6 in the form of quinonoid bases (anhydrobases), hemiketals (pseudobases), chalcones, and in traces in the flavylium cationic form, at a pH value above 7.5 predominantly in the form of anhydrobase anions, and as the pH value increases further, more hydroxyl groups dissociate in the anionic quinonoid base structure [9,26,27].

Anthocyanins are usually red in acidic media (pH < 3), violet in neutral media, and blue in alkaline media (pH > 7.5) [26,27]. However, it was shown that the extract of staghorn sumac fruits was red in acidic media at a pH of 1 to 4, brown at a pH of 5 to 7, dark green in alkaline media at a pH of 8 to 12, and yellow at a pH above 13 [9]. The reason for this unusual color change in staghorn sumac fruit in neutral and alkaline mediums could be its unique anthocyanin composition, with the prevalence of 7-O-methyl anthocyanins and some unusual proanthocyanins, especially the sumadins [4].

The different colors of the extract in different solvents can be explained by the different acidity during the extraction of the anthocyanins from the staghorn sumac. From the staghorn sumac fruit extracted in methanol and ethanol, more acidic compounds, such as phenolic acids like gallic acid [1,3,5] and organic acids, especially malic acid [1,2], were extracted with anthocyanins; therefore, the extracts were brownish-red, as the anthocyanins were predominantly in the form of flavylium cations. Fewer acids were extracted from the fruits in propanol, acetone, acetonitrile, and dichloromethane compared to the more polar solvents, so the extracts with only slightly acidic pH values, in which more anthocyanins were present in the form of hemiketals, chalcones, and quinonoid bases, were yellowish-brown.

In distilled water with a pH of 5.5, the extract was brownish-red, a similar color to the extracts in methanol and ethanol, indicating the presence of flavylium ions of anthocyanins. When the aqueous extract was added to a printing paste with a pH of 7.4, the color changed to a light brown as the pH was raised to a neutral medium.

Although the anthocyanins in the extracts of the various solvents were present in different forms and thus in different colors, all prints with these extracts on cotton or paper had a brownish-yellow hue. After curing the prints at high temperature, when the anionic carboxylate groups of the polymer thickener converted to carboxyl groups to act as an acid catalyst in crosslinking the binder that binds the dye molecules entrapped in its polymer film to the cellulose substrate, the prints on the substrates had a neutral pH, which is why they had the same color hue. The difference between the use of different solvent extracts for printing is reflected in the intensity and darkness of the color, the uniformity of the prints, and their fastness properties, which are explained below.

3.2. Fastness of Prints

The suitability of the ink for printing on paper or fabric must also be assessed based on the fastness properties of the prints. The results of the fastness tests of prints are summarized in

Table 3. Colorfastness of prints on paper to dry rubbing and light.

Dye Extract	Rubbing		Light
	Print Surface	Color Transfer to White Paper	Color Change of the Print
distilled water	unchanged	no	6
distilled water/Elastil T. paste	unchanged	no	3
methanol	unchanged	no	6
ethanol	unchanged	no	6
propanol	unchanged	no	6
acetonitrile	unchanged	no	6
acetone	unchanged	no	6
dichloromethane	unchanged	no	6

for paper and in

Table 4. Colorfastness of prints on cotton fabric to dry and wet rubbing, wet hot pressing, laundering, and light.

Dye Extract	Rubbing		Hot Pressing		Washing			Light
	Staining of Dry Cloth	Staining of Wet Cloth	Staining of Wet Cloth	Staining of Dry Cloth	Color Change of the Print	Staining of Cloth	Color Change of the Print	Color Change of the Print
distilled water	5	5	5	5	5	5	1	3–4
distilled water/Elastil T. paste	5	5	5	5	5	5	1–2	3
methanol	5	5	5	5	5	5	1–2	6
ethanol	5	5	5	5	5	5	3	6–7
propanol	5	5	5	5	5	5	4	8
acetonitrile	5	5	5	5	5	5	1–2	6
acetone	5	5	5	5	5	5	1–2	6
dichloromethane	5	5	5	5	5	5	4–5	6

for fabric.

The abrasion resistance of the prints on paper was evaluated by dry rubbing tests under very severe conditions (Table 3). These tests showed exceptional resistance of the printed surface, with no signs of abrasion of the ink from the surface. The observations showed a shiny stain on the tested prints, which is due to the lower abrasion resistance of the white paper used to rub off the print.

The prints on the fabrics showed excellent resistance to dry and wet rubbing, as well as to wet ironing (Table 4).

The prints on paper and fabric were very lightfast (grade 6) when printed with the extracts in all organic solvents and on paper, as well as with the aqueous extract (Table 3 and Table 4). The prints made with the extract in propanol had excellent light fastness (grade 8) on cotton fabric, while the prints made with aqueous extracts had only moderate light fastness (grades 3–4). The aqueous extract showed the highest degree of color fading on both substrates (grade 3) when Elastil Transparent printing paste was used, which in our case did not prove to be a suitable printing paste due to the unevenness of the prints. The study on the dyeing of cotton fabrics with the aqueous and methanol extracts of the staghorn sumac fruit showed lower light fastness properties of the dyeings (grades 3–4) for both extracts [11]. In our case, the dye in the methanol extract gave the print on cotton fabric a much better light fastness than the aqueous extract.

The wash fastness test for textile samples at 40 °C has shown that the fastness is influenced by the solvent used to extract the dye. The prints made with the aqueous extract discolored the most when washed (grade 1), followed by those in methanol, acetone, and acetonitrile (grades 1–2), and then in ethanol (grade 3). The low washing stability was also shown in the dyeing of cotton fabrics with the aqueous and methanol extracts of the staghorn sumac fruit [11]. The best wash fastness of the prints was achieved with the inks made from the dye extracted in propanol (grade 4) and dichloromethane (grades 4–5). With the smaller amount of extracted dye in dichloromethane, only very pale brownish-yellow prints were achieved, which is why they had better wash resistance than darker and more intense shades of other solvent extracts. Due to its lower extraction efficiency, its higher consumption due to its high volatility, and its toxicity, dichloromethane is not suitable for the extraction of anthocyanin dyes from the fruits of staghorn sumac.

However, uniform brown-yellow prints were obtained with the dye extracted in propanol, which showed good wash fastness and excellent light fastness properties on cotton fabric, indicating a possible application of this dye extract for printing on textiles.

The binder plays the main role in fixing the prints to the fibers. The rub and wash fastness of the prints depends on how strongly the polymer film of the binder adheres to the fibers. The propanol extract has a slightly higher viscosity compared to the other solvents [28] and may be more incorporated into the polymeric binder film, which may be thicker and affect better wash resistance and, due to its higher concentration on the fiber surface, better light fastness. However, these assumptions need further investigation.

The printing inks of the dye extracted with distilled water, which are produced from the printing paste of the individual components, and the printing inks of the dye extracted in ethanol and propanol are well suited for printing on paper due to the uniform prints and the rub and light fastness properties suitable for paper products. Ethanol, propanol, and, above all, water are also among the preferred solvents in the chemical industry in the search for less toxic options [25].

4. Conclusions

The dye extracts obtained from the red fruits of staghorn sumac by extraction in distilled water, methanol, and ethanol were brownish-red, in propanol and acetone brownish-yellow, and in acetonitrile and dichloromethane greenish-yellow. All these dye extracts can be used to formulate screen printing inks with a pigment printing paste. However, only the extracts in distilled water, ethanol, and propanol in dichloromethane produced uniform prints on fabric and paper.

The prints made with sumac fruit extract generally had brownish-yellow hues, except with the extract in methanol and ethanol, where more brownish-orange prints were obtained. The prints on cotton fabric were darker and more intense, with a more pronounced yellow color value than on paper.

All prints with inks based on the staghorn sumac fruit extract in different solvents on paper and cotton fabric showed excellent rub fastness. The prints on cotton fabric also showed excellent resistance to wet ironing. The prints generally had very good light fastness (grade 6) and even excellent light fastness (grade 8) on fabrics with the dye extracted in propanol. The wash resistance of the prints depended very much on the solvent used to extract the dye. When the inks were made from the dye extracted in propanol and dichloromethane, the wash fastness of the prints was good (grade 4).

It can be concluded that the printing ink produced from the dye extracted in propanol is an optimal choice for printing on cotton fabrics in terms of the intensity, darkness, and uniformity of the printed color as well as the fastness properties of the prints. The printing inks with the dyes extracted in propanol, ethanol, and distilled water are well suited for printing on paper. These results show how important it is to choose the appropriate solvent for the extraction of dyes from staghorn sumac fruits in order to achieve the best print quality and durability on the respective substrate.