Why does the temp of water matter when washing clothes?

With certain temperatures the fabric reacts by shrinking, fading etc. It really depends what you’re washing. What is it? – and I can refine my answer.

I was just curious in general. I always wash everything cold.

With cotton fabrics, washing in the hottest water cleans the best. However, it can clean the dye right out of the fabric. The notorious red shirt with the white underwear dyeing everything pink.

In general, whites go in hot, I do everything else in warm, since I don’t buy clothes that leech dye much.

Washing cold is always safe, but it might not get whites totally clean =)

I never wear white so I always wash in cold.

I’m kind of from the old school where the belief was that you couldn’t get things clean unless you used hot water. Not so anymore. The detergents of today are made to clean in cold water. I set my water temp on ‘warm’ & it comes out a tepid coolish temp. Hot water will also shrink & fade material, so it’s not a good choice. Warm or cold is the way to go, IMO.

Think back to science class if you’ve had one. When you are trying to combine one substance with another, there are certain factors you can control. Agitation, temperature, and time all influence dissolving. In the case of laundry you are trying to “undissolve” the stains and dirt away. More specifically you use a detergent which goes in there, finds the dirt particles, stick to it, then bonds to the water. Hot water makes it easier for the particles that comprise the stain to get loose and thus go away.

The problem is that dye is also particles, and when you increase the heat, you increase the chances of the particles loosening from the material. Then the detergent and water come in and move it all around. The dye really does love to stick to materials though, so it will adhere itself to any other material it can. This is why you get pink shirts when putting a red item into a load of white.

White clothing of course has no dye. This means you can apply a lot of heat to get out really rough stains and the cloth will be perfectly fine. Undergarments are often white not only because it’s less effort to not dye the item, but because you can get the really worn in stains and sweat out without risking any damage to the item.

Colored items should be washed in cold water to reduce any chances of having the dye run.

Black clothes are sometimes separated out because that black dye can also run, and that will taint all the other colors by shading them darker.

Nowadays detergents do a lot of the heavy lifting when it comes to cleaning our clothes, so it is OK to wash your whites with your colors provided you keep it cold. And since you use cold water, the chances of dye particles becoming loose is reduced, so if you’re lazy like I am you can put all your laundry together and have no problems with color transfer. That said, my whites could be whiter. But I don’t really care enough to go through the extra effort.

@dynamicduo Wow, you ARE brave in throwing everything all in together. I’d NEVER do that. For instance, the dye in blue jeans will transfer over onto white cotton. And you certainly don’t what to wash red in with anything else.

Towels will cause a lint situation.

I do believe there’s a reason for your not so white whites.

I don’t own blue jeans, so that’s fine with me. I put bright colors right in with whites and have no problems. Neither do I have problems with lint. Maybe you should just be a bit more brave, @jbfletcherfan :)

The whites thing was really a joke. My whites are perfectly white, save for the armpits of certain undershirts, but that’s because of the antiperspirant. In that case hot water and separate washing could help.

I wash everything in cold so nothing runs or shrinks. My clothes aren’t necessarily dirty, so I can’t comment on whether hot water cleans better than cold.