IMPORTANT UPDATE *Edited 27 June 2014*
In the post below I recommend medium weight interfacing suitable for coats. In further chats with the designer, I realise that this would NOT be suitable for the right and left fronts in particular and possibly for the entire jacket, depending on your fabric – something lightweight is needed. I asked the designer about this and she provided the following comment that explains it perfectly:
“I chose lightweight interfacing because I didn’t want to change the hand of the fabric, I just needed to add a bit of stability. The fabric I used was very soft and drapey, but heavy and with time under its own weight it would deform. So mostly I used the interfacing not to change the fabric, but to “hold it together” better. It is much different from the tailored jacket sewing when the goal is to make the fabric to look more like a shell.”
The original post continues below (with my adjusted recommendations in bold)…
You will often read experienced seamstresses comment about the importance of using the right interfacing to achieve a lovely result when sewing. I have certainly learnt this the hard way – using poor quality interfacing that either over-stiffens up my fabric, and not in a good way, or that really cheap thin stuff that you can pull apart with your hand and melts permanently to your iron at the drop of a hat.
So I had a couple of sewalong-ers ask about some more direction with interfacing so we decided to look around online and provide some quality links to “the good stuff” that is suitable for the kind of sewing we are doing – we need a good quality woven fusible interfacing that still maintains the nice drape of our fashion fabric.
For Australia –
I purchased a professional grade weft interfacing from Pitt Trading for $10/m. It is lovely and soft, does not need preshinking, and adds good body and support without adding stiffness or changing the hand or feel/drape of the fabric. They do not have it on their online store, but it can be purchased by phoning them. (Just ask for the professional grade interfacing [lightweight] suitable for using with [a drapey coat] suiting/coating and they will send you the right one).
You also should get good recommendations from places like Tessuti Fabrics who sell this one online recommended for coats and heavier fabrics. [EDIT: I would use the lightweight interfacing for your jacket left and right fronts and possibly your entire jacket, depending on your fabric. The white one is here, the black one is here]
Another excellent source for quality interfacing for Sydney is EM Greenfields, which is a sewing supply wholesaler but they do sell by the metre to the public. They ship to anywhere in the world and if you send an email to them detailing what you are after (a good quality [lightweight] woven fusible interfacing suitable for jackets/coats with drape) they will be happy to help out.
For the US readers –
Fashion Sewing Supply sells high-quality professional weft interfacing. The recommended one for coating and suiting is this one here. [The lightweight interfacing suitable for our purposes for the jacket fronts is here]. It is the company owned by Pam Erny, who wrote this tutorial about interfacing on Gertie’s Blog for Better Sewing.
Another recommended source is A Fashionable Stitch.
All of these links are for independent sewing companies that will be able to offer you advice about your particular fabric and project and recommend the best choice for you. It’s the kind of service that you don’t find in the larger chain stores and why I try to buy from these places. If you are not sure, phone before you order and have a chat, or order a swatch and test it on your fabric to be sure you are happy before placing your order.
For everyone worldwide –
If you really don’t want to buy online I highly recommend that you try to buy from an independent sewing shop like the ones listed above. Usually, the staff are extremely knowledgeable about their products and you will (in most cases) find that their recommendations are really helpful. If you take in a sample of your fabric and ask for professional interfacing, you should end up with the “good stuff”.
What NOT to use –
Don’t use non-woven cheap chain store fusible. Don’t choose anything really lightweight or too heavy or anything stiff. If you can pull it apart with your fingers and looks like really thin felt I would steer clear.