The white streaks are more than likely detergent left in the clothes. Be sure and wash/rinse with full load of water and right amount of detergent. I put white vinegar in the rinse dispenser to help remove detergent from clothes. Do not over stuff the washer. Dry in dryer using the wash/wear setting. HANG shirts on clothes hangers immediately after dryer stops. Heat & gravity will help smooth out wrinkles while hanging. Taking shirts out of dryer just short of being completely dry & hang works well too. IF you are hang drying the shirts, there will be too many wrinkles to iron out. Not a good idea to iron knit shirts, it will stretch them as a rule. If you do use an iron be sure and use the steam setting and lightly move iron over the shirts....White marks can also be from mineral build up inside the iron that spits out off and on. Be sure and use distilled water in the iron for steaming. Follow instructions for cleaning inside of the iron.

White marks also could be from spray starch.

white marks come when I crank the heat up on the iron. I did a test today I washed them... immediately threw them in the dryer ...immediately took them out and hung them and then after about 15 minutes ironed them. They are 100% cotton Greg Norman shirts or Nautica shirts. I have less trouble with cotton blend shirts. My daughter says to use a squirt bottle and mist the shirt before ironing it but that did not help that much. she also said I should use fabric softener but I don't like the way it smells. This is the iron maybe I have it on the wrong setting what setting wrong... do you recommend? here is the pink shirt she ironed still looks wrinkly to me.if you want me to steam the sucker tell me the best setting to do that I was just afraid cuz shirts a cool iron only!

Normally, t-shirts don't require ironing. Do you take them out of the dryer promptly? You could also try wool dryer balls instead of dryer sheets. They are supposed to help reduce wrinkles.

https://www.amazon.com/gp/product/B083LHV14M/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

I have darker cotton shorts that would also streak when ironed. I now iron them inside out.

Misting, whether from a spray bottle or adding water to the iron (see manual) is also helpful.

Are you using tap water in the iron? If so, clean the water tank of iron and then use distilled water. On top of your iron the button on the left will shoot steam when pressed and the button on the right will spray a mist of water in front of the iron.

Some thoughts and suggestions:

"Iron cool" can be a CYA on the part of the clothing manufacturer. It rarely works for me, especially with natural fibers.

I iron all my cotton and cotton/Lycra dressy tee shirts on the Wool setting with some steam.

Check your iron's owners manual. If it says use tap water, that is what you need to do. Very few require distilled water anymore; it can actually harm newer irons, over time. I haven't used distilled water in thirty years.

The first pic of the red top . . . could that long white mark be where there was a seam under that layer of fabric while ironing? Looks like that to me. If so, it could be some crocking of the dye when the heat of the iron goes over that bump.

Try ironing your shirts inside out.

Try taking them out of the dryer before they are completely dry and iron immediately.. Otherwise, those wrinkles can be "baked" in. I tumble dry mine on Low for five to eight minutes, then they finish drying on a rack. They are ironed later. Not everyone has the floor space for one, though.

Finally, the white stuff could be residue of the optical brighteners in detergents. Perhaps the detergent is overdosed, IDK. I use a detergent with no optical brighteners on my colors and darks, as often as possible, to prevent the fading effect caused by OBs.

HTH

Iron your shirts, cotton included, inside out. Also, while you might put the iron on “Cotton” setting for your 100% cotton shirts, lower the heat to “synthetic” and use a damp “pressing cloth” if you are ironing anything with polyester in it. Inside out is the best answer to your problem of persistent wrinkles in flat ironing of stretchy cottons.

PS: The “white” that you are seeing isn’t white. I believe it is scorch marks on your fabric, especially your seams. Use a pressing cloth over the seams when ironing them. (A pressing cloth is something my mother always used...A piece of old cotton from her discarded white pillowcases that she always had folded on the ironing board.)

here is what I think I found that works but it's still a pain in the butt!

First I purposely a shrunk some of this stuff that's why I left it in the dryer so long. However it's still a pain in the neck to run over the dryer and grab stuff out at just the right time.

White mark on seems... yes that's what I'm noticing ...pockets, seems, stiched emblems.... and every now and then if I rotte the iron too quickly... it leaves a mark.

Yes I discovered ironing inside out seems to work better but sometimes I still have to lightly go over the front then.

Some shirts go better than others! These particular ones... sadly I bought four or five in different colors.. next time I'll grab one and try ironing at first hahaha.

The ones that were giving me the most difficulty I set the iron on the linen setting filled it with water and started steaming real good and I also sprayed with a spray bottle ...by the way I use tap water in spray bottle and iron ....said it was okay for iron.. This seemed to work.

sure is a lot of trouble though!

Thanks!

For cotton knit tops I don't rotate the iron, Iset in place and steam and move to another place.
Cotton 100%, needs a hot iron and it needs to be dampened before ironing. If it' a button, woven rather than knit, start with the sleeves....smoothed out....then the back over the board and then the fronts one at a time....do the yoke over the end of the hoard and do the collar last....in the right side so you see any wrinkles and starting at the point and moving to the center.
And really....fabric softener will do a lot to eliminating your problems.....try many and find one that doesn't leave a lingering scent.

Use a bit of fabric softener to release the wrinkles. A Rowenta iron and a damp press cloth will do a good job. Some white marks are actually press marks from fabric folds underneath, as if you are ironing a wrinkle. Buy some dark knit fabric such as navy or black, wash it, dry it, and experiment.

You may also need a good solid ironing board with a pad and cover. If you are using an old board, try replacing the cover and check the pad underneath to see if it has heft or has disintegrated. A good source of ironing equipment is the Vermont Country Store. https://www.vermontcountrystore.com

The book "Home Comforts" has an extensive section on ironing. https://www.amazon.com/Home-Comforts-Science-Keeping-House/dp/0743272862

Mist the clothes with a spray mist, kinda' fold them up & place in a plastic bag for a few minutes...Long enough for the moisture to evenly penetrate. Then iron.

Back in the old days, we 'sprinkled' clothes and put them in a zippered plastic bag. (Usually these items were the ones that were starched--but didn't have to be starched.)

This technique works well if you're using spray starch, too. Spray, fold up, let sit for a bit.

Where do you live, OP? I am bringing you all my shirts so you can practice.

LOL Far, far away!

mist the clothes and put them in a bag! Am I on Little House on the Prairie! I'm a guy! I don't have time for this. I can pay my mortgage online how can ironing be so comllicated! lol..I'm going to use a little fabric softener and use the listing method and I'll get a new ironing board cover cuz ours is probably 20 years old...

I don't have time for this.

LOL! I don't/ won't iron tee shirts! The only other person who I know that 'used to' iron t-shirts is my brother. He's a weird one, my brother. :-)

Ironing is a skill with a lot of techniques and clever equipment, much of which is historical rather than current. Choose what works for you. Part of your difficulties may lie in trying to get a flat finish on fabrics that contain spandex or other elastic fibers. It's the spandex's job to return the fabric to its original state, so fabrics with spandex are never going to be as flat as pure cotton.

@ci_lantro : Thanks for the reminder photo. I see the Vermont Country Store still sells those sprinkler caps. Now they are plastic and shown with a huge plastic soda bottle, alas, not the traditional aluminum top and glass Coke bottle that was easy to shake. Spray mister bottles can spray quite evenly but they don't get the fabrics as wet as the old sprinkler bottles.

Very few people probably own sleeve boards any more.

I admire you for trying. Some people (not me) are truly skilled at ironing. For sure practice and experience help a lot. What I do, is I cheat. By that I mean I do a pretty good job doing the sleeves, nice, smooth and crisp. The rest, I do lightly. I find after sitting and wearing for a few minutes, the body doesn't look so crisp but those sleeves---they sure stay crisp.

Lol it gives the suggestion that the whole shirt was beautifully ironed.

YMMV (your mileage may vary).

I’ve recently discovered Best Press. It's available in various light scents. It seems to add something similar to sizing which sort of restores the fabric's original finish.

Best Press