The width of you scarf base depends on how wide your fabric is, of course you can buy mulberry silk scarf blanks like the ones I have listed here. I also usually start my scarves at around 1.8 - 2 mt long. This allows for the shrinkage if you cover the entire piece with wool. The more wool you cover the silk fabric with the more it will shrink , so go a little larger than you need. Allowing for about 30-40% shrinkage for scarves is about what you are aiming for.
If your fabric has raw edges and you would like to neaten them up, just gently press them over the edge with a cool iron and run some wool under the raw fabric edge and then lightly over the top of the same edge to cover it and give it a lovely little ruffle all around. I felt with my hand dyed superfine Tasmanian Merino Wool all the time and know how it will felt. It is really important that you use wool that you know will actually felt easily. A simple test with some wool and a little soapy water and gentle rolling it into a ball for about 50-75 rolls in your hand over the kitchen sink will soon tell you that it is starting to felt or that it is pulling apart.
How much wool would I need?
Some other wool and fibre estimates...
And yes, they are estimates! because we all lay out a little differently and I generally over estimate a little to make sure you don't run out before you finish laying out the fibres!
Wool Felted Hats, depending on the size and shape:
I usually allow approximately 100 grams of wool tops, the amount depends on the design of the hat. I would also allow 20 grams of Mulberry Silk fibres for decoration and adding some quirky fun to your hat.
Slippers, you want these thick and warm!
Pair of slippers 200 grams of wool tops depending on the size of your foot and how high you want them on your leg. Put more wool layers on your slippers, they will need it. Also are you after a shoe style or an Ugg style? You might also want to consider using a stronger wool type like my Corriedale wool roving/tops for the outside of the slippers because its harder wearing.
Jackets and vests
These can vary widely depending on what you are doing, some thick bulk jackets are made from raw fleece and weigh a tone! but other beautifully made thin vests are light and easy to wear. Experimentation, planning and practice is the key to these. Most people will have to do a workshop to get these right.
If you are making a medium size light weight Nuno vest would need about 200 grams of wool tops to go with your silk fibres and any silk fabric pieces.
Where as, a medium size winter weight (All Wool) jacket is around 400 - 500 grams of wool tops plus you Mulberry silk fibres for decorations and details.
Above all have fun with your felting and enjoy what ever you make even if it is not quite what you intended... even I have a few of those lurking in the cupboard reminding me gently occasionally to stop and think a little more before jumping in the deep end! But isn't that all part of the fun??