This has probably been asked a dozen times but...?
I use a flammable felt stiffener from Parkins UK, not cheap at £20.00 plus VAT plus postage for 500ml???
But try as I do, and work it in to the felt it always leaves behind white marks/residue??
Is there really another alternative other than the expensive flammable stiffens that don't leave these marks!
I'm sure i've read somewhere about watered down PVA which is sprayed onto the inside of felt?
Any suggestions greatly appreciated:-)