I just bought this fantastic T-shirt , yellow - which unfortunately is
at least 2 sizes to BIG , my question now is how can I reduce the size
, i.e. SHRINK this T-shirt without having to take it apart, cut it and
alter it !!!???

Hi tomasmuscionico,

Re: How can I shrink clothes?
http://www.madsci.org/posts/archives/nov2001/1004993484.Ot.r.html

"Contrary to popular perception, water alone does not shrink clothes. It's 
the combination of mechanical action, high temperatures and water that 
causes fibers to contract. Excessive drying can also shrink clothes. High-
tech washers and dryers with computerized controls limit the risk of 
shrinkage in modern water-based cleaning.

To shrink some jeans, I would suggest washing in hot water especially when 
they're new, then drying on high heat and leaving them in the dryer 
afterwards.  Cotton is easy to shrink.  Synthetics are usually not 
shrinkable."

=================================================

Dryer Shrink Clothes
http://www.magicyellow.com/forums/General/m10023.htm

"Dry them on hot temperature in the dryer. Set it to high.It should
work. Cotton shrinks the most."


"Pretty simple actually, all you have to do is place them in the
washer on the highest temperature setting, wash. Then place them in
the dryer on the highest temperature setting, and let them stay in the
dryer for a while after the cycle is over, that should shrink them a
little."


"Wash them on the hottest setting and dry them on the hottest setting,
but when youre drying them throw in a Dryel sheet or something."

=================================================

How To Buy T-Shirts - Shrink Resistance and Special Finishes
http://ohioline.osu.edu/ccues/tshirt.html

T-shirts should be shrink resistant to one or two percent to maintain
proper size. All-cotton T-shirts, even high quality ones, if
unfinished, may shrink as much as five percent which is more than a
size change. So buy a larger size to compensate for such shrinkage.
Blended T-shirts tend to shrink less.

=================================================

Why do cotton and wool shrink when you wash them?
http://www.cottoninc.com/cottonfacts/homepage.cfm?PAGE=25
 
"There are two kinds of shrinkage. Progressive shrinkage occurs when
the fiber itself shrinks. Wool fiber shrinks a little more each time
it is washed, which is why wool is usually dry cleaned. Relaxation
shrinkage is when the fabric shrinks. It is caused by the tension
applied to yarns and fabrics during construction. The tension is
released when the fabric is washed or steam pressed, causing it to
shrink to its natural size. Most cotton fabric shrinkage occurs during
the first wash."


Best regards,
tlspiegel

To add to tlspiegel's excellent answer:

I have had some success in shrinking cotton knit items by ironing them
with a hot iron while they were VERY damp (almost soaking wet). Push
the iron from the outer edges of the garment toward the inside so that
the garment is not inadvertently stretched as you iron. Keep ironing
until the garment is nearly dry, then throw it in a very hot clothes
dryer.

Note that this may cause uneven shrinkage, and the neck, sleeves, and
hem of your T-shirt may be a bit wavy as a result. I once reduced an
XXL shirt to approximately the size of an L by using this method. It
only works with 100% cotton, not poly blends.

Hang it in my closet.  Clothes hung in there shrink like crazy with no
effort at all.