How does HTV actually work? (Siser)

[Jack Coletti 1]

Hi Folks,

I curious to know if Heat Transfer Vinyl uses glue to stick to fabric - or is it melted on - or both?

I am trying to improve the longevity of my HTV garments - and would like to better understand how the Siser Easyweed material that I am using actually works.  I have read articles that suggest that there is an "adhesive" that gets "activated" by the heat press - but I don't fully understand how this works. Regular vinyl, of course, uses a pressure activated adhesive - which is easily felt on the back of the material.  But, when I handle HTV, I don't feel any adhesive at all (other than the adhesive on the liner).  It seems like the HTV actually melts on to the fabric.

I'd like to understand how it works so I can find the sweet spot of temperature and pressure on my particular heat press.  It seems that I get better adhesion when I raise the temperature and increase the pressure.  But I am concerned that I might either be harming the adhesive in the long term (which I'm not even sure if it exists) - or that the increased heat may cook the plasticisers out of the vinyl and make it more brittle and short lived. Another consideration is that some laundry detergents might harm the adhesive - if it exists.

Thanks!

[Wildgoose 4,200]

I do a LOT of HTV work and Siser is my fav. You are correct in your assessment that there is adhesive on the back side. I suggest you get an infrared heat temp gun and check your platen temp. Many platens can have cool spots and many of the heat readings on them are way off. Heck even my $2000 Fusion was 40deg off and required an adjustment. 

I tend to lean toward the longer end of the dwell time like 12-15 seconds I do 15 and if you have a cool spot on your platen increase the temp until that spot is up to the recommended 305deg unless its on an obscure corner that doesn't see much contact. The Siser people will tell you you can adhere with even less temp than the 305 but I don't like to have to worry about it. I have tested Siser Easyweed at much higher temps without a failure. You WILL begin to see some of the adhesive start to bleed out along the edges particularly in layered work but no one without a trained eye will ever even notice. I wondered if this would cause too much to escape and thereby trigger a failure but I have never had one from overheat. 

Pressure is also a key element. Swing away presses tend to develop more even pressure than clams unless the clams have a center point load. Watch out for thick collars and sewn seams. They will hold your platen up and cause failures. Heat press pillows are the cure for that application. I have not seen any problem with over pressure other than again possibly causing some of the adhesive to bleed out at the edges.