A novel algorithm for easy-care laundering of linen fabrics: A cleaner solution to the wrinkling problem during care

Abstract

In this study an attempt was made to improve the wrinkling behavior of linen fabrics encountered during washing in washing machines with steam generators was tried to be achieved. To improve the wrinkling behavior of linen fabrics while still maintaining a gentle washing action, different combinations of steaming steps were inserted into the laundering process. Moreover, individual and interactive effects of the spin level, as well as those of heating in rinsing or in softening steps, upon average shrinkage and average smoothness ratings of the laundered linen products were evaluated after performing relevant standard tests. An alternative algorithm was created offering even better performance in terms of smoothness rating with acceptable average shrinkage after laundering, offering an increase in the smoothness rating from 1.40 to as high as 3.63, with a decrease in shrinkage from 5.50% to as low as 3.45% for the levels studied. Heat application was found to have positive and significant effects on the average smoothness rating.

Keywords

linen fabric smoothness rating shrinkage washing machine washing algorithm effect of steaming easy-care hot rinsing spinning hot softening

There are novel studies regarding the enhancement of the cleaning performance of the laundry process without giving any damage to textiles.^1–4 Many programs have recently been developed as a function of washing machines as a result of research regarding the washing algorithms for the fabrics produced from synthetic and natural fibers.⁵ Due to the fact that time is one of the most important phenomena in daily activities, decreasing the time required for the laundering process and elimination of the additional processes before and after the laundering process has become the most significant and considered topic to be achieved for a washing machine laundering program. Wrinkling, which causes a waste of time because of the long ironing process required to remove wrinkling, is the main issue of the laundering process. Making improvements to the wrinkling problem encountered in the laundering process would absolutely reduce the time needed for ironing.

Linen is one of the most preferred fabrics for the summer. Due to the increase in perspiration rate, garments are washed frequently in the summer, and wrinkling developed in the laundering process becomes the most common problem for linen fabrics. Furthermore, it is a known fact that linen products, like those manufactured from other natural cellulosic fibers, have a tendency to wrinkle. In order to decrease or overcome wrinkling during daily use and care, special chemical finishes are applied to linen during manufacturing, and more are used on demand. Therefore, various studies related to anti-crease finishing of cellulosic fibers appear in the scientific literature. Anti-crease finishing treatments are applied to cellulosic based products in order to eliminate wrinkling, with additional benefits including dimensional stability and pile resilience; however, these also bring some general disadvantages including loss of abrasion, tear and ripping strength, handle and elasticity, graying during washing, and some other disadvantages including the release of formaldehyde (a carcinogen), reduction of light fastness, shade changes on colored fabrics, yellowing, chlorine retention and undesirable odors (resembling the smell of fish), depending on the chemical and application method applied. The studies related to anti-creasing are mostly about the cross-linking of cellulosic fibers, either with the use of a self-cross-linking product, which results in a polymerized finish in the pores of the fibers and blocks the penetration of water into the fiber, or one that cross-links with cellulose molecules, hindering the swelling of the cellulose fibers by forming a cross-link between the hydroxyl groups of adjacent cellulose molecules.⁶ In recent studies, cross-linking of the cellulosic chains has been achieved with chemical reactions; and some nanotechnological and biotechnological methods have also been applied for achieving cross-linking.^7–21 Some researchers offered partial carboxymethylation followed by cross-linking,^7–11 while some others used microwaves for curing¹² and UV irradiation¹³ or gamma irradiation^10–11 for cross-linking. Titanium dioxide was shown to be a useful agent.^13,16–20 An extensive review is made by Harifi and Montazer.²¹

These chemical processes can be hazardous, both for human health and for the environment, because there is a risk that chemical wastes might leak into the water supply during production and application of chemicals to the material, as well as due to detachment and release during use and care. Because of this, the main objective of this study was to make some improvements to the shrinkage and wrinkling behavior of linen fabrics without any need to use chemicals and nano-particles during and after the laundering process, while still maintaining gentle washing of the fabric. Development of a novel linen laundering algorithm via selection of better levels of laundering parameters and insertion of steaming steps resulting in better shrinkage and wrinkling performance has previously been reported.²² In this study, with the insertion of different combinations of the steaming steps into the laundering process, different laundering profiles were created, and by doing this it was intended to further minimize the shrinkage and wrinkling problem of linen fabrics. Moreover, the effects of heating in rinsing and softening steps, as well as that of spinning level were studied. It was previously revealed that additional heat during laundering resulted in decreased wrinkling. Therefore, it is expected that use of hot water in the place of cold water during rinsing or softening as well as a combination of steaming steps would further decrease wrinkling. Individual and interaction effects of spinning level, as well as those of heating in rinsing or softening steps on average shrinkage and average smoothness rating of the linen products were evaluated. The best laundering profile in terms of shrinkage and wrinkling among those studied was selected for minimizing these risks, and thus a new algorithm was developed for linen in laundering machines possessing a steam generator. Moreover, optimization plots were constructed for mapping the desirability at an average smoothness rating of 3.50 with a minimum shrinkage value.

Experimental

Materials

The linen fabrics that were used in the study were chosen according to a market survey and face-to-face interviews with the linen fabric manufacturers. The fabrics chosen for the study were 100% linen fibers; an example of the linen fabrics is shown in Figure 1. The 100% pure linen fabrics had many more problems with wrinkling when compared with linen fabrics consisting of different percentage additive fibers, so it was decided that these would be used in the study.

Figure 1.

An example of the linen fabric used in the study.

The fabric construction was plain weave, since it is a much more stabile structure. The properties of the linen samples used can be seen in Table 1.

Table 1.

Properties of the linen samples used

Linen sample type	Density (warp × weft) (per cm)	Yarn count (warp and weft)	Mass/area (g/m²)
Plain weave	22 × 22	Ne25	110

Filling (stowing) load, which was used with the linen test samples in this study in order to represent the amount of clothes in a washing machine during the laundering process, was substituted by cotton fabric. White etamine fabrics were chosen as the filling (stowing) load, since they were known not to contaminate black-colored linen fabrics with white fibers during laundering.

The detergent used in the laundering processes was of IEC standard code IEC60456. The ingredients of the detergent were 77% base powder with enzyme and foam inhibitor, 20% sodium perborate tetrahydrate as bleaching agent and 3% tetraacetylenediamine as the activator of the bleaching agent. For a load of 3 kg, 76 g of detergent was used.

Machines and equipment

The two washing machines used for the tests were identical. Each was a frontloading machine, with a loading capacity of 8 kg, having a double water inlet and a maximum spinning speed of 1200 rpm. The machine was equipped with a single-nozzled steam generator, located at the back of the tumbler, which could produce steam in a few minutes when full of water; it could supply a continuous flow of steam for almost 15 minutes. Therefore, the generator could be used periodically during and between the laundering steps of the whole process. The machine had multi-sensors for loading weight, steam temperature, water amount, rinsing, rotational speed (revolutions per minute (rpm)) and voltage.

Method

In the preliminary work, since the main problem had been defined as the wrinkling behavior of linen fabric and the solution was steam application to the fabric in the washing machine from a steam generator, different steaming steps were added between the laundering steps of the washing machine (see Table 2) in order to obtain new laundering profiles. While doing this, firstly, the effects of laundering parameters (water amount, the rate of mechanical action and total time of mechanical action/total time of washing (ED), temperature, and rotational speed) on average shrinkage and average smoothness rating were investigated, and better levels determined. These were a water amount of 16 l, ED 50%, temperature 40℃, and rotational speed 52 rpm, the combination of which offer a lower average shrinkage and a higher average smoothness rating among the levels of the parameters studied. Secondly, to the laundering profile taking the previously determined better levels of laundering parameters as constants, steaming steps were inserted before cold washing, before first spinning, before rinsing, before second spinning, before softening, before last spinning and after last spinning. As a result of this, a total of seven different new laundering profiles, each incorporating a single steaming step, were created (see Table 3). The laundering process was repeated three times for each of the seven laundering profiles with each of the two identical washing machines, simultaneously. Shrinkage and smoothness rating measurements were done after the first and third laundering processes. When all of the results of the tests were examined, the steaming steps of the laundering profiles, which offer better improvement, were chosen, mostly considering the average shrinkage and average smoothness rating results after the third laundering process. Therefore, the laundering profiles, each having a single steaming step inserted after the last spinning step (Profile 7), after the softening step (Profile 6), after the second spinning step (Profile 5) and after the first rinsing step (Profile 4) were all found to positively affect the wrinkling behavior of the linen fabrics, their individual effects following the order Profile 7 > Profile 6 > Profile 5 > Profile 4. It was shown that the insertion of additional heat results in the formation of less wrinkling during laundering.²²

Table 2.

Laundering steps used.²²

Step	Total time (min)
Cold washing
Heating
After heating
First spin
Rinsing
Second spin
Softening
Last spin
	76

Table 3.

Steaming steps inserted between the steps of the laundering process.²²

Steaming step	Laundering process step
Steaming (Profile 1)
	Cold wash
	Heating
	After heating
Steaming (Profile 2)
	First spin
Steaming (Profile 3)
	Rinsing
Steaming (Profile 4)
	Second spin
Steaming (Profile 5)
	Softening
Steaming (Profile 6)
	Last spin
Steaming (Profile 7)

In this study, considering the four best profiles previously determined, different combinations of steaming steps were inserted to the laundering process by combining the second, third and fourth ranked best laundering profiles (Profile 6, Profile 5 and Profile 4, respectively) with the best laundering profile (Profile 7). Moreover, the effect of heating in the rinsing or softening steps, as well as that of spinning on the average shrinkage and average smoothness rating results of laundered linen products were evaluated. It was previously stated that insertion of additional heat during laundering resulted in decreased wrinkling. Thus, it was expected that utilization of hot water instead of cold water during rinsing or softening as well as a combinations of steaming steps would result in a higher average smoothness rating. Full factorial experimental design was constructed, according to Montgomery, by combining low, medium or high spinning and heating in the rinsing or softening steps with laundering profiles comprising different combinations of steaming steps (see Table 4).²³ Therefore, eighteen new laundering profiles were determined and the laundering process was repeated three times for each of the profiles, with each of the two simultaneously working washing machines, which will be shown to be identical. For the low spin, the first and second spinning steps were eliminated and only the last spinning step was performed at 800 rpm. For the medium spin, the first and second spinning steps were performed at 600 rpm and the last spinning step was performed at 1000 rpm. For the high spin, all of the medium spinning steps were performed for prolonged durations. Shrinkage and smoothness rating tests were performed after the third laundering process. All test results were assessed by with MiniTab® software, single and interaction effects examined and optimization plots constructed for mapping the desirability at an average smoothness rating of 3.50 with minimum shrinkage value. After all of the tests and analysis, the best new laundering profile among those studied was determined.

Table 4.

The new laundering profiles determined by the combination of steaming steps, different levels of spinning and heating in the rinsing or the softening steps

New profile ID	Heating	Spin	Steaming combinations
RL76	Rinsing	Low	7–6 (Profile 7 and Profile 6)
RL75	Rinsing	Low	7–5 (Profile 7 and Profile 5)
RL74	Rinsing	Low	7–4 (Profile 7 and Profile 4)
RM76	Rinsing	Medium	7–6 (Profile 7 and Profile 6)
RM75	Rinsing	Medium	7–5 (Profile 7 and Profile 5)
RM74	Rinsing	Medium	7–4 (Profile 7 and Profile 4)
RH76	Rinsing	High	7–6 (Profile 7 and Profile 6)
RH75	Rinsing	High	7–5 (Profile 7 and Profile 5)
RH74	Rinsing	High	7–4 (Profile 7 and Profile 4)
SL76	Softening	Low	7–6 (Profile 7 and Profile 6)
SL75	Softening	Low	7–5 (Profile 7 and Profile 5)
SL74	Softening	Low	7–4 (Profile 7 and Profile 4)
SM76	Softening	Medium	7–6 (Profile 7 and Profile 6)
SM75	Softening	Medium	7–5 (Profile 7 and Profile 5)
SM74	Softening	Medium	7–4 (Profile 7 and Profile 4)
SH76	Softening	High	7–6 (Profile 7 and Profile 6)
SH75	Softening	High	7–5 (Profile 7 and Profile 5)
SH74	Softening	High	7–4 (Profile 7 and Profile 4)

Test process

AATCC test method 124 ‘Standard test method for smoothness appearance of fabrics after repeated home laundering’²⁴ was used for assessing the appearance of smoothness by three trained observers of the flat fabric specimens after repeated home laundering. This method can be used for any washable fabric to evaluate the appearance of smoothness. Assessment according to this method can be done for fabrics of any construction, such as woven, knit and nonwoven. Rating values between 1 and 5 are given, and a high rating value represents less wrinkling on the specimen. Nine observations made on each test fabric (three grades for each of three test specimens) were averaged. In this study, average smoothness ratings were rounded to the closest two decimal places, and this average value is the unit of measure of this test method.

AATCC test method 135 ‘Standard test method for dimensional changes of fabrics after home laundering’²⁵ was used for the determination of dimensional changes of the fabrics when subjected to home laundering procedures used by consumers. In this standard method the dimensional changes of the fabric specimens subjected to home laundering care are measured using pairs of benchmarks placed on the fabric before laundering. The shrinkage values are calculated as percentages. According to the standard method, the fabric specimens are required to have dimensions of 50 cm × 50 cm and the area between the bench marks needs to be 35 cm × 35 cm. However, the fabric specimens used in this study had dimensions of 38 cm × 38 cm and the area between the benchmarks was 25 cm × 25 cm. The equation for the shrinkage calculations is shown below.

Shrinkage (%) = \frac{((Markedarea beforelaundering) - (Markedarea afterlaundering))}{Markedareabeforelaundering} \times 100

IEC 60456 test method ‘Standard test method for clothes washing machines for household use, methods for measuring the performance’²⁶ states the methods for measuring the performance of clothes washing machines for household use, with or without heating devices utilizing a cold and/or hot water supply. In addition to this, the international standard deals with appliances for water extraction by centrifugal force (spin extractors) and can be applied to appliances for both washing and drying textiles (washer-dryers) regarding their washing-related functions. In this method, measurement of the color and loading of the fabrics are mentioned. Fabric loading instructions for this method were applied. In order to bring the weight of the fabric to 3 kg as specified in the standard, 24 pieces of white etamine fabric were loaded into the machine chamber.

Results and discussion

In this study, which aimed to minimize the shrinkage and wrinkling of linen fabric by inserting different combinations of the steaming steps determined into the laundering process, the better laundering profile in terms of the resulting average shrinkage and average smoothness ratings was selected. Eighteen different profiles that were created with the steaming step combinations were combined with heating in the rinsing or the softening steps and different levels of spinning, details on which can be seen in Table 4. Average smoothness rating and average shrinkage results are presented in Table 5. It should be noted that both average shrinkage and average smoothness rating results reported are those measured after the third laundering, as it is known that the performance results for fabrics after multiple launderings are generally more significant as a result of their being loaded with extensive stress during manufacturing, and analysis of measured performances after multiple launderings would be more representative of the effects of the parameters studied.²²

Table 5.

Average shrinkage and average smoothness ratings for eighteen new laundering profiles

New profile ID	Average shrinkage (%)	Average smoothness rating (1–5)
RL76	3.45	3.31
RL75	3.70	2.72
RL74	4.24	3.28
RM76	3.89	3.19
RM75	4.86	3.44
RM74	4.13	3.31
RH76	4.14	3.22
RH75	3.98	3.63
RH74	4.11	3.13
SL76	4.21	3.56
SL75	4.21	3.50
SL74	3.87	3.31
SM76	4.39	3.28
SM75	4.41	3.50
SM74	4.16	3.50
SH76	4.33	3.38
SH75	4.21	3.53
SH74	4.68	3.41

Before presenting individual and interaction effects of steaming combinations, spinning levels, hot rinsing or hot softening on average shrinkage and average smoothness rating values, it will be shown that the two washing machines used in the study are identical in their performance in terms of their effect on resulting average shrinkage values and average smoothness ratings.

As shown in Figure 2, the average shrinkage values for machine 1 and machine 2 are 4.66% and 4.63%, respectively, for a confidence interval of 95%. In addition to this, standard deviations are 0.39 and 0.43, respectively, showing that there is no significant difference between the two machines working simultaneously, meaning that they are identical in their effects on average shrinkage results.

Figure 2.

Mean of machines’ effect upon average shrinkage after third laundering.

The effect of the two simultaneously working machines on average smoothness rating after third laundering can be seen in Figure 3. According to the analysis, average smoothness ratings for Machine 1 and Machine 2 are 3.30 and 3.28 for a confidence interval of 95%, with standard deviations of 0.23 and 0.29, respectively. Similar to their effects on average shrinkage, the two machines showed no significant difference in their effects on resulting average smoothness rating. Thus, the two machines appear to be identical, and both shrinkage and smoothness rating results coming from laundering by these machines will be considered to be statistically from the same population.

Figure 3.

Mean of machines’ effect upon average smoothness rating after third laundering.

The individual effects of heating (hot rinsing and hot softening), spinning (low, medium, and high), and steaming combinations (7–4, 7–5, and 7–6) on average shrinkage after the third laundering are shown in Figure 4. Considering the individual effects of hot rinsing or hot softening, the average shrinkage values are 4.61% for hot rinsing and 4.68% for hot softening, which are very close to each other. It is obvious that hot rinsing and hot softening have similar effects on average shrinkage after the third laundering. When the results on the individual effects of spinning levels on average shrinkage after the third laundering are considered, it is apparent from Figure 4 that low-level spinning has the lowest average shrinkage value, 4.51%, as expected due to lower mechanical agitation causing lower average shrinkage (i.e. the first and second spinning steps are omitted, and the final spinning step is run at as low as 800 rpm). However, application of medium and high spinning levels resulted in a slightly higher average shrinkage of 4.71%. It is known that low-level spinning decreases the amount of detergent removed in the laundering process, which decreases laundering rinsing performance. On the other hand, high-level spinning is generally considered to be bad for the service life of the washing machine, especially the motor. Keeping these facts in mind and taking into consideration that the resultant average shrinkage values are only slightly different, medium-level spinning has been chosen as the better spinning level, offering better laundering performance. The average shrinkage values for different steaming combinations were found to be 4.52% for the 7–6 steaming combination, 4.78% for the 7–5 steaming combination and 4.63% for the 7–4 steaming combination, with very parallel standard deviations of 0.41, 0.40 and 0.39, respectively. In parallel with the effects of heating and spinning, the effect of steaming combinations resulted in only slight differences in terms of average shrinkage. It is apparent from Figure 4 that the range of average shrinkage results coming from different profiles is very narrow, regardless of the effect of the parameter studied. The main reason for this is the selection of better levels of machine parameters as a constant for all new profiles (water quantity 16 l, ED 50%, temperature 40℃, and rotational speed 52 rpm), which appears to be the main reason for the decrease in average shrinkage. Moreover, Profile 7, which incorporates a steaming step after the last spin, is included in each profile, as one part of the steaming combination, which was previously shown to cause an additional decrease in shrinkage during laundering, superior to that offered when other steaming steps are considered individually.²²

Figure 4.

Means of the effects of hot rinsing, hot softening, spinning levels, and steaming combinations on average shrinkage after third laundering.

The individual effects of heating (hot rinsing and hot softening), spinning (low, medium, and high), and steaming combinations (7–4, 7–5, and 7–6) on the average smoothness rating after the third laundering are shown in Figure 5. It is apparent that low-level spinning results in a slightly lower average smoothness rating (3.24) when compared with those of medium- and high-level spinning (3.31 and 3.33, respectively). It is believed that an increase in fabric stiffness as a result of unlevel distribution of the washing bath after low-level spinning causes the increase in smoothness rating to be limited. Considering the aforementioned handicaps regarding high-level spinning, along with inconsiderable differences in average smoothness rating for alternative spinning levels, medium-level spinning appears to be the preferred alternative, offering better laundering performance. Taking the individual effects of hot rinsing or hot softening into consideration, the average smoothness rating values are 3.20 for hot rinsing and 3.38 for hot softening, both of which represent a very remarkable improvement when compared with the average of the preliminary study (which was 2.52). On the other hand, unexpectedly, when the effects of steaming combinations are investigated, it has been observed that the 7–6 steaming combination, which is the combination of steaming steps whose individual effects were shown to be superior to those of the others in our previous study, was not found to have the highest contribution to the average smoothness rating (3.27). It is believed that for the 7–6 steaming combination, all excessive stress loaded on the fabric during laundering prior to the sixth step (coming mainly from cold washing, warm washing, first spinning, rinsing, second spinning, and softening) is fixed on the fabric at a given level, and a considerable portion of it is released after the application of steam. When another steaming step is applied (seventh step) much of the stress, with the exception of that coming from the last spinning, is already released, leaving little work for steam application to do at the seventh step, meaning that their individual effects will not be additive. Considering the 7–5 steaming combination, it is apparent that an amount of stress is fixed on the fabric (coming mainly from cold washing, warm washing, first spinning, rinsing, and second spinning), and much of it released during the fifth step, but there are still some laundering steps during which stress is to be applied on the fabric, until the seventh step. In this steaming combination, there is a higher share of work to do for the seventh step, when compared with that of the 7–6 steaming combination, resulting in an average smoothness rating of 3.36. Finally, for the 7–4 steaming combination, the stress loaded until the fourth step (coming mainly from just cold washing, warm washing, first spinning, and rinsing) is released, while some of it might still be fixed on the fabric, but there are a number of laundering steps (second spinning, softening, and last spinning) until the fabric finally encounters a release of stress at the seventh step, meaning that there is much work to do for the seventh step, resulting in an average smoothness rating of 3.25. Considering all the facts mentioned above, it is wise to expect that when steam is applied just after any spinning step, its effect on recovery of the newly formed wrinkles is higher, and when there is one or more additional laundering steps following a spinning step, the wrinkles are highly prone to becoming fixed, bringing a greater burden for the consequent steaming step. Thus, a better combination of the individual steaming steps is of those that are following any of the individual spinning steps: the 7–5 steaming combination. According to the preliminary and current studies it is apparent that heat application, especially when applied subsequently to any one of the spinning steps of the laundering process, have positive and more significant effects on average smoothness rating (i.e. steaming after any one of the spinning steps or heating during softening rather than during rinsing).

Figure 5.

Means of the effects of hot rinsing, hot softening, spinning levels, and steaming combinations on average smoothness rating after third laundering.

Considering the interaction effect of heating–spinning (see Figure 6), it was found that the hot rinsing-low-level spinning couple has the minimum shrinkage value (4.31%). This is rather as expected, as hot rinsing helps the fabric to stay in a more relaxed state, while a low level of spinning causes a lower amount of stress on the fabric to be released, resulting in a higher dimensional stability. The second rank in the minimum shrinkage value is observed at the meeting point of hot softening and medium-level spinning (4.67%). Selection of hot softening and medium-level spinning would be more favorable in the determination of the best new laundering profile amongst those studied, when their individual effects on both average shrinkage and average smoothness are also considered. It is apparent from the interaction between heating and steaming that shrinkage is very much affected for alternative steaming combinations with hot rinsing, especially with the 7–6 steaming combination, which appears to be the only steaming combination offering better average shrinkage values than any steaming combination with hot softening (see Figure 6). When heat is applied during rinsing, the softening step is performed using cold water, which brings additional loading on the fabric just before the sixth steaming step, which makes the application of the 7–6 steaming combination more effective for decreasing resulting shrinkage. On the other hand, the interaction between hot softening and any of the steaming combinations offers more relevant average shrinkage values without significant differences. When high-level spinning is applied during laundering, it is apparent that selection and application of any of the three steaming combinations does not significantly affect the resulting average shrinkage. A low level of spinning resulted in lower average shrinkage regardless of the steaming combination applied, as expected. Finally, a medium level of spinning resulted in higher average shrinkage (4.96%), still not exceeding that achieved in the previous study (4.96%). It appears that limited improvement is possible in terms of shrinkage, regardless of the levels of the parameters among those studied. Thus, the average smoothness rating will be the important factor in the selection of better levels of parameters when offering the best new laundering profile.

Figure 6.

Interaction plot of the means of effects of steaming–spinning, heating–spinning and heating–steaming on average shrinkage after third laundering.

Interaction effects of heating–steaming, spinning–steaming, and heating–spinning on average smoothness rating values are shown in Figure 7. Considering the interaction effect of heating and spinning, the effect of hot softening on the resulting average smoothness rating is more consistent and higher than that for hot rinsing, regardless of the spinning level applied. When a medium level of spinning is applied together with hot softening, the resulting average smoothness rating reaches the maximum among those studied (3.39). The heating–steaming interaction plot once again shows that the effect of hot softening on the smoothness rating is higher than that for hot rinsing, regardless of the steaming combination. The highest average smoothness rating value (3.49) is achieved when hot softening is applied together with the 7–5 steaming combination. Finally, when the interaction effect of spinning and steaming is considered, it is apparent from Figure 7 that the 7–5 steaming combination offers higher average smoothness rating values when compared with the other two steaming combinations, with the exception of low-level spinning. This opposite inclination is rather expected, as low-level spinning only incorporates the final spinning step, located just between the sixth and seventh steaming steps; thus, the combination of these two results in a higher average smoothness rating. When the effects of a high and medium level of spinning on the average smoothness rating is compared, the averages gained when high-level spinning is applied appears to be slightly higher than that offered by medium-level spinning for the 7–5 steaming combination (3.58 and 3.42, respectively). All of the average smoothness rating results presented, ranging from 3.10 to 3.58, outscore the smoothness rating achieved in our previous study (2.52). The main reason for this appears to be the incorporation of heat in rinsing or softening, and using steaming combinations. Taking the individual effects of parameters on the average smoothness rating as well as interaction effects into consideration, selecting medium-level spinning, the 7–5 steaming combination, and hot softening for offering the best new laundering profile would be appropriate.

Figure 7.

Interaction plot of the means of effects of heating–steaming, spinning–steaming and heating–spinning on average smoothness rating after third laundering.

When all of these results were considered, the most suitable profile for recovery from wrinkling of linen fabrics during the laundering process with an acceptable average shrinkage was found to be the SM75 profile, which possesses hot softening, medium-level spinning, and the combination of seventh and fifth steaming profiles.

A further effort may be to question the effectiveness of the proposed algorithm in reaching a desired level of smoothness rating with minimum shrinkage possible. A common way of accomplishing this is via utilizing a desirability study. Individual and composite desirability assess how well a combination of variables satisfies the goals that has been defined for the responses. Individual desirability (d) evaluates how the settings optimize a single response; composite desirability (D) evaluates how the settings optimize a set of responses overall. Desirability has a range of 0 to 1. Here, 1 represents the ideal case; 0 indicates that one or more responses are outside their acceptable limits. It is shown in Figure 8 that the individual desirability for average shrinkage is d = 0.62727 with an average value of 4.7455%, while that for the average smoothness rating is d = 0.91667 with an average smoothness rating of 3.4167. On the other hand, composite desirability for reaching an average smoothness rating of 3.50 with a minimum average shrinkage is D = 0.8497. Such a high composite desirability figure shows that by an application of the selected levels of parameters, it is highly probable that an average smoothness rating of 3.50 with minimum shrinkage can be achieved.

Figure 8.

Optimization plot for minimum shrinkage and smoothness rating of 3.50.

Individual desirability (d) as well as composite desirability (D) values for minimum shrinkage and smoothness rating of 3.50 are given in Figure 8.

Conclusions

It would be most practical to recover the wrinkles formed during daily use and care during laundering at home; in this study an attempt was made to enhance the wrinkling behavior of linen fabrics encountered during laundering action in washing machines possessing steam generators. To improve the wrinkling behavior of linen fabrics while still maintaining a gentle laundering action, different combinations of steaming steps were inserted into the laundering process. Moreover, individual and interaction effects of spinning level, as well as those of heating in the rinsing or softening steps, on average shrinkage and average smoothness rating of the linen products were evaluated. The best laundering profile in terms of the resulting average shrinkage and average smoothness rating was selected for minimizing these risks, and a new program was developed for linen in laundering machines possessing a steam generator. In total, 18 different profiles were created by MiniTab® Design of Experiments software, and the best, with hot softening, medium-level spinning, and having the steaming steps inserted before the softening step and after the last spinning step, was chosen. Average shrinkage and average smoothness rating values for a linen fabric laundered using a conventional cotton program were 5.50% and 1.40, respectively, while those laundered using better levels of laundering parameters reached 4.96% and 2.10, respectively. When steam is incorporated, the same figures reached averages of 4.96% and 2.52, while after the insertion of steaming combinations and hot softening as well as selection of medium-level spinning it resulted in averages as good as 4.41% and 3.50, respectively. It has been shown that the application of heat, especially when applied subsequently to any one of the spinning steps of the laundering process, has positive and more significant effects on the average smoothness rating.

Footnotes

Acknowledgments

The authors would like to sincerely express their highest appreciation and gratitude to the members of the system improvement team of Arçelik Washing Machine Plant, Arçelik Washing Efficiency Laboratory, and Arçelik Textile Technologies Laboratory.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

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