Comparison of Cleaning Treatments for Conservation and Restoration of Cotton, Wool and Silk Fabrics

RESULTS AND DISCUSSIONS

It is well known that aesthetically yellowing is the most prominent outcome of ageing, indicating to the changes happening at the molecular level of the fibre. Most of the times, this yellowing is caused by a layer of fibre deterioration by-products or the broken molecular chains on the fabric surface (Cardamone, 2000). The process of molecular chain incision cannot be reversed, however, aesthetics of the fabric can be improved by removing these deterioration products from the surface of the fabric and bringing up the lower-lying, unbroken molecular chains. Although broken molecular chains do not contribute much to the fabric strength, their removal might expose the unbroken ones to the surface and slightly hasten the process of ageing. Thus while attempting this process a balance has to be created between restoring aesthetics and conserving fabric strength

1. Cotton

   • Tensile Strength

     It is evident from Table 1 that cotton undergoes a strength reduction of 31% in the warp direction and 33% in weft direction after ageing. None of the wet cleaning treatments has been able to restore this lost strength fully. It can be further seen that fabric loses further 11% strength in warp direction after home-laundry. Further, ultrasonic wash also leads to high strength reduction. Loss in Breaking Load is least in case of dry-cleaning, closely followed by enzyme wash. However, the trend changes in the weft direction where all other treatments except home laundry, reverse some breaking load lost due to ageing. The reversal is most in case of dry-cleaning followed by an ultrasonic wash. Enzyme wash neither deteriorates the fabric strength further nor restores it. This further explains that warp sizing plays a strong role in fabric deterioration

     	S.No	Unaged Sample	Aged Sample	Home Laundry	Dry Cleaning	Enzyme Wash	Ultrasonic wash
     							5mins	8mins	11mins
     SD	0.67	0.60	0.62	0.08	0.66	0.29	0.22	0.48
     CV %	8.46	10.98	12.73	1.62	12.91	5.94	4.60	10.31
     % Change	–	31.16	11.31	5.47	6.57	12.04	13.14	15.69
     Breaking Load (Weft) (N/m2)	Average (8 samples)	7.40	4.95	4.46	5.59	4.99	5.30	5.48	5.11
     SD	0.90	0.50	0.43	0.53	0.61	0.54	0.43	0.44
     CV %	12.17	10.07	9.58	9.49	12.29	10.19	7.80	8.59
     % Change	–	33.08	9.90	-12.93	-0.81	-7.07	-10.71	-3.23
     Extension % (Warp)	Average (5 samples)	13.00	5.33	3.33	3.33	6.67	8.00	10.00	7.00
     SD	1.83	0.75	0.00	0.00	0.00	0.75	0.00	0.75
     CV %	14.04	13.98	0.00	0.00	0.00	9.32	0.00	10.65
     % Change	–	59.00	37.52	37.52	-25.14	-50.10	-87.62	-31.33
     Extension	Average	20.21	8.33	3.33	6.67	8.54	9.79	14.38	8.54
     n % (Weft)	SD	3.01	0.00	0.00	0.00	0.59	0.59	1.77	0.59
     CV %	14.91	0.00	0.00	0.00	6.90	6.02	12.30	6.90
     % Change	–	58.70	60.02	19.93	-2.52	-17.53	-72.63	-2.52
     Change in Colour	WI	-178.99	-193.37	-212.56	-187.21	– 176.68	– 182.34	– 187.45	-183.86
     Change in WI	–	14.37	33.56	8.22	-2.32	3.34	8.45	4.86
     YI	97.75	103.39	102.65	101.35	97.70	100.56	101.21	100.50
     Change in YI	–	-5.62	-4.90	-3.59	0.05	-2.81	-3.46	-2.75
     Table 1: Effect of Cleaning Methods on Breaking Load, Extension and Colour of Cotton Fabric

   • Looking at Extension% values, it was realised that fabric loses 59% of its extension value after ageing, both in warp and weft direction. Wet Cleaning Treatments like home-laundry and dry-cleaning further reduce extensibility in warp direction by 37%. Interestingly, loss in weft direction is high in case of home laundry but reduced in dry-cleaning. This indicates that unsized weft yarns, after ageing, are at a greater risk of damage by alkaline detergents. Although enzyme treatment reverses the loss in extension by 25% in the warp direction and 3% in the weft direction, ultrasonic wash indicates slightly better results in terms of reversing extension % loss caused by ageing. It can be seen from Table 1 that enzyme wash seems to balance out the two tensile parameters the most. Further SD and CV% values establish the validity of the experiments conducted. However, final conclusion can be deduced only after looking at the spectrometer observations.

   • Colour Change

     It can be seen from Table 1 that enzyme wash manages to bring the cotton fabric closest to its original, unaged condition, both in terms of WI (Whiteness Index) and YI (Yellowness Index). Ultrasonic wash- 5 minutes stands close second, followed by 11 minutes and 8mins treatment time in the ultrasonic wash. Home-laundry and dry-cleaning further reduce the WI, although they counteract yellowness to a certain extent. It can be safely concluded from the above data that enzyme wash, i.e., Cellulase treatment is the most balanced option to sanitize aged cotton fabric and restore its whiteness to a certain extent. Although treatments like ultrasonic wash seem promising at some parameters, strength loss in the warp direction is too high to classify it safe for washing cotton fabrics. On the other hand, home-laundry by alkaline reagents has been proved to be most harmful to aged cotton fabrics, followed by dry-cleaning.

2. Wool

   • Tensile Strength

     It has been observed in the previous section that wool undergoes the least loss in strength by 20yrs of ageing. As per the readings in Table 2 the loss in the warp direction is close to 2% and in weft direction 10%. However, wet-cleaning treatments might alter this to a certain extent.

     	S.No	Unaged Sample	Aged Sample	Home Laundry	Dry Cleaning	Enzyme Wash	Ultrasonic Wash
     							5mins	8mins	11mins
     Breaking Load (Warp) (N/m2)	Average (5 samples)	21.6	21.22	21.42	19.62	19.56	18.78	18.6	18.58
     SD	0.81	0.86	0.41	0.83	0.26	0.85	0.58	0.41
     CV %	3.76	4.05	1.91	4.22	1.33	4.51	3.11	2.20
     % Change	–	1.76	-0.94	7.54	7.82	11.50	12.35	12.44
     Breaking Load (Weft) (N/m2)	Average	13.25	11.9	10.7625	11.025	11.55	9.65	9.8125	10.875
     SD	0.69	0.36	0.43	0.60	0.16	0.46	0.23	0.43
     CV %	5.21	3.05	4.00	5.42	1.39	4.80	2.34	3.99
     % Change	–	10.19	9.58	7.31	2.94	18.91	17.56	8.57
     Extensio n % (Warp)	Average	14.33	16.67	12.33	11.00	13.33	16.67	14.00	13.33
     SD	1.49	0.00	0.91	1.49	0.00	0.00	1.49	0.00
     CV %	10.40	0.00	7.40	13.55	0.00	0.00	10.65	0.00
     % Change	–	-16.33	26.03	34.01	20.04	0.00	16.02	20.04
     Extension % (Weft)	Average	27.08	31.67	23.33	23.33	20.83	18.96	15.83	16.67
     SD	3.05	2.52	0.00	1.78	2.36	1.98	1.54	0.00
     CV %	11.28	7.96	0.00	7.64	11.31	10.44	9.75	0.00
     % Change	–	16.95	35.75	35.75	34.23	40.13	50.02	47.36
     Change in Colour	WI	-231.97	-255.15	-254.05	-251.99	-250.94	-251.85	-253.74	-252.01
     Change in WI	–	23.18	22.08	20.02	18.97	19.88	21.77	20.04
     YI	107.41	116.90	115.08	114.99	115.88	116.34	117.12	116.46
     Change in YI	–	-9.49	-7.67	-7.58	-8.47	-8.93	-9.71	-9.05
     Table 2: Effect of Cleaning Methods on Breaking Load, Extension and Colour of Wool Fabric

   • Interestingly, home-laundry of wool in non-ionic detergent conserved the strength in the warp direction, in terms of breaking load. However, in the weft direction, the strength loss is close to 10%. Strength loss in case of dry-cleaning and enzyme wash is equivalent at 7% in the warp direction, but weft direction registers much-reduced loss in weft at 2%. Ultrasonic wash at all three durations is causing higher loss of strength as compared to other wet cleaning treatments, both in warp and weft direction. Coming to the loss in extension%, ultrasonic wash again reflects unbalanced results between warp and weft. However, home-laundry, dry-cleaning and enzyme wash register balanced loss in both warp and weft with enzyme wash faring slightly better than the rest of the two techniques.

   • Colour Change

     The data (Table 2) corresponding to WI and YI values clearly reflect the superiority of enzyme wash treatment to all other treatments of wet cleaning. Where maximum whiteness is restored by wash, yellowness is most reduced by dry cleaning, closely followed by home-laundry and enzyme wash. Ultrasonic treatment at 5mins also reflects values close to an enzyme wash. Correlating the data obtained by tensile tests and spectrophotometric readings, it can be concluded that all three, home-laundry by non-ionic detergent, dry-cleaning and enzyme wash by Protease enzyme, stand equivalent chances of sanitizing wool fabric with minimum strength loss and some restoration of fabric colour. Ultrasonic wash does not provide clear data, as the readings contradict between warp and weft direction, as in the case of cotton fabric. Thus ultrasonic wash cannot be recommended in its present detail.

3. Silk

   • • Tensile Strength

       Table 3 suggests 24% loss in strength in warp direction and 28% loss in weft direction after ageing. As per the data collected post-wet-treatments, it can be seen that dry-cleaning and ultrasonic wash at 8mins provide the most balanced results, closely followed by an ultrasonic wash at 11mins.

       	S.No	Unaged Sample	Aged Sample	Home Laundry	Dry Cleaning	Enzyme Wash	Ultrasonic Wash
       							5mins	8mins	11mins
       Breaking Load (Warp) (N/m2)	Average (5 samples)	20.04	15.32	15.06	16.88	15.90	16.84	16.34	15.72
       SD	0.40	1.23	1.86	1.37	2.99	1.08	0.66	1.36
       CV %	2.01	8.01	12.32	8.09	18.80	6.39	4.03	8.67
       % Change	–	23.55	1.70	-10.18	-3.79	-9.92	-6.66	-2.61
       Breaking Load (Weft) (N/m2)	Average (8 samples)	29.68	21.24	24.75	27.48	20.26	26.31	23.63	21.39
       SD	2.35	1.45	2.42	1.73	0.82	4.44	3.43	3.36
       CV %	7.91	6.81	9.79	6.30	4.03	16.86	14.53	15.73
       % Change	–	28.44	-16.53	-29.38	4.61	23.87	-11.25	-0.71
       Extension % (Warp)	Average (5 samples)	18.00	15.00	10.00	11.33	14.00	19.00	16.67	17.00
       SD	0.75	0.00	0.00	0.75	1.49	0.91	0.00	1.39
       CV %	4.14	0.00	0.00	6.58	10.65	4.80	0.00	8.20
       % Change	–	16.67	33.33	24.47	6.67	-26.67	-11.13	-13.33
       Extension % (Weft)	Average (8 samples)	21.67	20.21	14.17	14.38	10.00	19.58	18.13	18.33
       SD	2.82	2.26	1.99	1.77	0.00	0.77	0.59	0.00
       CV %	13.00	11.19	14.06	12.30	0.00	3.94	3.25	0.00
       % Change	–	6.74	29.89	28.85	50.52	3.12	10.29	9.30
       Change in Colour	WI	-201.48	-195.67	-206.63	-222.95	-208.91	-209.32	-212.64	-208.84
       Change in WI	-5.81	5.16	21.47	7.43	7.84	11.16	7.36
       YI	96.55	98.51	100.96	103.51	101.14	102.32	103.76	101.98
       Change in YI	-1.96	-4.41	-6.96	-4.59	-5.77	-7.21	-5.43
       Table 3: Effect of Cleaning Methods on Breaking Load, Extension and Colour of Silk Fabric

4. Enzyme wash, home-laundry and ultrasonic wash at 5 minutes do not illustrate uniformity of results in warp and weft direction, thus cannot be recommended in their present form.

5. Colour Change

   WI and YI readings of silk treated with different wet-cleaning treatments demonstrate conflicting results (Table 3). It can be seen that uniformly, all wet-cleaning treatments are reducing whiteness of the fabric and increasing yellowness to some extent. Thus, comparison in terms of restoration of colour is not possible in this case. The discussion, therefore, can only revolve around sanitizing the fabric at a minimum colour loss. It can be seen that dry-cleaning and ultrasonic wash at 8mins are causing a maximum alteration in fabric colour. At the same time, home-laundry renders minimum damage in that respect. Rest all treatments alter fabric colour to a similar extent.

Combining the results obtained by tensile tests and spectrophotometer readings, ultrasonic wash at 5 minutes and dry-cleaning can be described as most suitable for sanitizing an aged silk fabric.

CONCLUSIONS

Thus it can be seen that no one method, in general, can be considered suitable for cleaning of aged fabrics made from different fibres. Enzymatic cleaning by Cellulase enzyme has been proved to be the least harmful and most efficient method of cleaning aged textiles. Therefore, Enzyme wash in aged cotton fabrics is the most balanced method of sanitization without much loss of strength and performance parameters. However, in the case of wool fabric; home laundry, dry cleaning and enzymatic cleaning by protease enzyme prove equally beneficial in cleaning the fabric with minimum strength loss. This can be attributed to the inherent nature of the wool fabric to resist damage due to deterioration. On the other hand, ultrasonic wash at 5 minutes presents the most suitable cleaning option for silk fabric. The findings of this section confirm that fibre constitution has a profound role in deciding suitable cleaning treatments for aged fabrics.

AUTHORS

1. Kanika Sachdeva: Department of Fabric and Apparel Science, Lady Irwin College, University of Delhi, India
2. Mona Suri: Academic Vice-president, Royal University for Women, Bahrain
3. Simmi Bhagat: Reader, Department of Fabric and Apparel Science, Lady Irwin College, University of Delhi, India

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