This article outlines some of the effects of water temperature on cleaning performance in a clothes washer - specifically, the removal of various types of stains. The experimental data below serves to illustrate the importance of proper water temp, and one of the advantages of having an internal heater in a clothes washer (that can reach these "very high" wash temps). [See also the related FAQ article, "Clothes Washers - Internal Heater Advantages ??".] This is a simple test, washing various "tough" stains with a measured dose of a given detergent and no pre-treatment.
[Report first posted in the Appliances Forum by Alice (Alice_61) on 22 September 2002 in the "Technical Suds Part 2" thread - thanks, Alice!]:
The effect of temperature on stain removal in the Miele W1918A washer
I washed a stain strip with a 10 lb. load of cottons and 2 oz (by weight) of Tide HE powder in the Intensive Cotton cycle, using each of the available temperatures on the Miele W1918A: 85F (30C), 105F (40C), 120F (50C), 140F (60C), 155F (70C), 180F (80C), and 190F (90C).
First, a few general comments before I get into the particulars of specific stains:
1. Before these stain tests, I had choosen wash temperatues strictly according to the user's guide. Because we have so few whites, I had never done a wash above 140F. I was willing to go to higher temperatures with the test load, because it consisted of old clothes and rag material. After trying the 190F wash, I was very impressed at how colorfast most items were. There were a couple of things that colored the drain water (colored jeans), so I replaced them with other items for the test load.
2. The white background of the stain swatches was much whiter at the higher wash temperatures. This didn't become too noticable until 155F, and increased to a very bright white at 190F. It seems from this and the better stain removal of certain stains, that the bleach was becoming more active at higher temperatures.
3. I used some old, cheap (the 12/$3.00 type) wash clothes for the test load. We had gotten to the point of using them as cleaning clothes. After about 25 washings with the test load, many at high temperatures and some with considerable detergent doses, these wash clothes were very clean and bright. I happened to find some identical wash clothes stashed away and compared them to these very washed ones. Not only were the very washed ones much cleaner and brighter than the old ones, they did not seem any more faded than the old ones. In fact, they looked a whole lot better. Perhaps greying of the old washclothes made them seem less colored. I think this and #1 alleviates my concern about fading at high temperatures, at least for colorfast items.
4. The detergent perfume smell is considerably reduced by washing at high temperature. I didn't really notice this until the last two loads (180 and 190F) so I can't say exactly at which temperature this occured.
Blueberry juice and grape juice: These stains certainly responded well to increased temperature. I'll describe the results for blueberry juice. Grape juice is similar. At 85 and 120F, the stain was not oxidized (it remained blue) and not much was removed. At 120F oxidation started (turned brown) and the stain was lighter, though still with distinct edges at 120. At 155F and above, the stain was lighter and more diffuse. By 190F, the stain was still a light brown but one has to look for it.
Tomato sauce: This stain also benefited from heat. At 85F, it was a yellow stain. It got progressively lighter up to 155F, then stayed about the same: a light, but still noticable stain. In another test, the remainder of this stain was removed by soaking in a sodium percarbonate solution.
Avacado: This oily stain also benfited from heat. It progressed from a fairly dark grey-green at 85F to a much lighter shade at 180F.
Grass stain: This result was interesting to me because it was not what I expected. I had expected that grass stain would do better at a low temperature, since it is a protein based stain. However, the stains from 85 to 140F varied some in intensity, but were visible. The stains at 155F and above were not visible.
Blood: Likewise, this protein based stain was almost, but not completely removed at 85, 105, and 120F. It was completely removed at higher temperatures. In addition, the white was quite a bit whiter at higher tempertures.
Chocolate syrup: All the washes left about the same intensity stain, faint, but clearly visable. In a different experiment, I was able to remove the remaining chocolate stain by soaking it in a sodium percarbonate solution.
Dirt (clay): This common stain proved to be a very difficult stain to remove completely. The stain seemed to show a little response to temperature. The stain left for 85, 105, and 120F were a prominent orange. It was slightly better for 140 and 155F. For 180 and 190F, the stain was better, but still noticeable. Later bleaching with sodium percarbonate did not improve the stain. Soaking in white vinegar afterward did not, either. I plan to try a rust remover and a couple of pretreatments.
Used motor oil: This is a really tough stain. As expected, the stain improved with higher temperatured. At 85F, the stain was quite dark and by 190F, it was about 1/2 as dark, but still quite noticeable.
Stain removal of all of the stains, with the exception of chocolate syrup improved at higher temperatures, often temperatures above that usually recommended for colored clothing. I would like to find an easy way to test for colorfastness, since high temperature is a powerful stain removal aid. In choosing between washers with various top temperatures, it is useful to know what difference in stain removal the top temperature might make. For those of us challanged weekly by stained laundry, it seems a very high temperature would be a plus.