I noticed one time with a certain white shirt that the area of the heat press platen turns into a light yellow.

Since it was not caused by the paper I thought may be the temperature was to high or the time to long.

After washing however that yellow area became white again and is no longer visible.

Anyone experienced the same?

Some time later I found that washing was not required to avoid the yellowing of the platen area.

I assume that the fabric becomes extremely dry after heat press and therefore it shows a yellow shining. If I sprayed a little water onto that area the yellow was gone.

Hi there
Since I work in textiles and weaving industry I think this problem could be found in some of the white fabrics,, specially 100% cotton
You know the raw cotton original color is creamy or yellowish a bid
To make it white, we do bleach it (we don’t dye it like any other color)
Now, bleaching is different quality. Some dye houses do an excellent bleaching that withstands washing and Ironing and some use cheap bleaching materials that will not withstand such a thing.
What happened exactly is that you have exposed your fabric to heat and pressure which is like super heating your fabric (extreme ironing).
I guess your fabric was not bleached well. That’s why you might experience this some of fabrics and not all.

Regards

An excellent input Ziad. That could explain indeed a lot in this matters.

Thanks,
Jan

Wow Ziad that is interesting. Can you explain more?

Ok guys
I will just share with you my small experience in dying
Been working in this field for 8 years now
Making white color is called bleaching which is removing any color from the cotton fibers ( no colors means white)
For cotton fabrics we use oxygen bleaching
For colors we use dyes, colored pigments that are inserted into the cotton yarns under certain pressure and temperature.
Dyes are different types exactly like different types of heat transfers, and each has pros and cons

Now, what’s important to know about dyes is the following:
1- It’s Resistance to washing with hot water
2- It’s Resistance to detergents (washing)
3- It’s resistance to Ironing and fraction
4- It’s resistance to Human perspiration
5- It’s resistance to Ultraviolet (Sun Exposure)
Each of the above criteria is measured in 1 to 5 scale ( 1 = low) (5 = high)
When we dye or bleach any fabric we chose a dye that fits the usage of the fabric.
For example, if we are dying a fabric that’s is going to be used as cloth, we should concentrate on the criteria 1,2,3 and 4 . 3 out of 5 for criteria no.5 will be very satisfactory.
If we are going to dye a fabric which will be used as a curtain, then we should concentrate on criteria no.5 ( curtain will be exposed to sun all time) it will not be exposed to human perspiration for example
so if your fabric gets yellowish after washing for example, them the bleach used was not resistance to detergents alkaline. And so on
Dyes are different qualities
Cheap dyes produce weak unstable colors

Any question am ready to answer