Pattern Notes on Simplicity 8578 – Robe a la Francaise Dress Pattern

A couple years ago now we worked with Simplicity to create a Robe a la Francaise pattern (Simplicity 8578) based on Abby’s sacque in The American Duchess Guide to 18th Century Dressmaking. When that pattern came out, I wanted to use it to make my own, but the gown got relegated to the UFO pile. Well, I’ve pulled it out again, determined to finish it, and while this post of notes and fixes is late in coming, I’m hoping it will help others who are making this pattern too. So here goes…

Differences Between the Book Gown & The Simplicity Pattern

Because Simplicity patterns have to be accessible for machine sewists and non-historical-costumers, we made some adjustments to Simplicity 8578. I knew that Simplicity would be writing the instructions and that things would have to be able to be put together with a sewing machine using modern methods such as bag lining. There was also a challenge with pattern tissue size – there is a set dimensions and restriction on the number of pieces of large tissue that could be included in the pattern. I tried to anticipate all of these issues.

Machine Sewing vs. Hand Sewing – The biggest difference, obviously, is the method by which the gown is sewn, and this is inextricable with the order of construction. The Simplicity pattern calls for bag lining and primarily machine stitching with a bit of hand sewing while the book gown is entirely hand sewn.

Stomacher – The Simplicity pattern calls for a comperes front stomacher that is stitched in at the sides of the gown and hooks at center front. This closure *is* historically correct (though you may wish to button or pin the center front), and it eliminates the tricky pinning at the sides. The book gown has a separate stomacher that pins in. It is completely up to you which method you choose – both are correct.

If you don’t care for the sewn-in comperes stomacher on the Simplicity pattern, make a separate one easily! Then you can change out the look whenever you like.

Gown Skirt Side Gore – The Simplicity pattern combines the gown skirt front piece and the side gore into one piece, whereas the book gown keeps these pieces separate. The reason for this is that historic fabric widths for silk were only about 20 inches wide, so to get the width for the skirt hem, separate gores were cut and seamed. For the Simplicity pattern, and modern fabric widths, I combined the gore and the skirt front to simplify the construction process.

Gown Skirt Front Edges Turned Back – Simplicity unfortunately omitted the dotted line indicating where to turn back the skirt front edges for the lovely triangular shape showing the petticoat. There *are* extant gowns that have straight front edges, so it’s not historically incorrect, but it is a difference between the Simplicity patterns and the book gown.

Sleeve Hems – Instead of using the straight-bottom sleeve like in the book, I drew in a curved sleeve hem to accommodate the crook of the arm. Both sleeve shapes are historically correct.

Known Issues & Fixes For Them

Too-Short Gown Skirt – Simplicity’s standard model block/size has a height of about 5’4″. No additional hem allowance was added to the gown skirt, so if you are over 5’4″ the skirt front edges come up too short.

Easy Fix – Extend the hem of all of the gown skirt panels (front skirt, gown back) as long as necessary for your height, and then some, for turning up the hem. It’s better to have it much too long than not long enough. You can determine the length needed easily by measuring from waist to floor over your pocket hoops, and adding a few inches for good measure.

If you, like me, have already cut your gown skirts and they are too short, piece in extensions to the hem. You’ll need to unpick the bottom 6 inches or so of the skirt seams and add extra fabric on, then re-seam. I added 6 inches extra to the front and side of my gown skirts, which is more than I needed, but I wanted to have extra to work with just in case. I know this feels sucky but remember – “Piecing is Period, Period

I am 5’6″, and about 5’8″ in my 18th century shoes, so I needed to add quite a bit to the bottom edges of my gown skirt. I should have measured before I cut, but I obviously didn’t! If you’re in the same boat, remember that it is totally fine to piece. SO many original gowns have piecing, and a finished gown of the right length will make you way happier than unfinished and too short!

Too-Long Petticoat – This isn’t really an issue, but it’s something to check. Don’t rely on where the pattern tells you to turn up the hem – it’s going to vary for each person. You want the petticoat to be somewhere around the top of your shoes.

Easy Fix – If you’re quite tall, add extra to the petticoat hem before cutting out. For everyone, put the petticoat on over the pocket hoops and all underpinnings before hemming, and mark where the hem should be. You can do this on a dress form too.

The hem of the petticoat should end up between the top of your shoes and your ankle bones-ish.

Gown Skirt Turn Backs – As I mentioned above, there are no instructions for turning back the front edges of the gown. This is a personal choice, so you don’t have to do it, but if you’d like more of the petticoat to show, it’s an easy adjustment.

Easy Fix – put the underpinnings, petticoat, and gown on a dress form (or have a friend help you with this), *before* you trim the gown. Fold back the front edges of the gown skirt to the inside, less at the top and more at the bottom, until it’s hanging nicely and showing as much of the petticoat as you like. There are instructions and photos for this in the American Duchess Guide book too.

Folding back the front edges of the gown skirt to show more of the petticoat.

Sleeve Length & Elbow Curves –  The curve of the sleeve hem, where it curves upward to allow for bending the arms without rucking up the sleeves, may not be in the right place for you (I struggled with this). Your sleeve may also be too long.

Easy Fix – These two aspects of 18th century sleeves are highly individualized, so *make a mockup* of the sleeve before you cut it out. The simplest solutions is to cut the bottom of the sleeve off straight like the pattern in the book, which fixes both issues – no need to re-draw the arm bend placement, and the sleeve is shortened to where it needs to be.

Option 2 – If you like the curve in the hem, pull the sleeve muslin on to your non-dominant hand side, make sure the shoulder point and underarm are in the right place, and then mark where the crook of your arm and elbow are. Rough in the new curve. Take the sleeve muslin off and redraw the new curve placement.

Stomacher/Stay Hooks – This one is actually just kindof funny. Simplicity misunderstood the purpose of the hooks on the stays and assumed the stomacher was meant to hook to them.

Easy Fix – Just omit those hooks. They serve no purpose.

I hope the above notes are helpful to you as you make the Robe a la Francaise of your dreams. Please feel free to share this with anyone else planning to use the pattern, too!


* Simplicity 8578 Sacque Gown + Petticoat works best and is intended to be worn with Simplicity 8579 Shift + Stays + Pocket Hoops. Both patterns work splendidly well with The American Duchess Guide to 18th Century Dressmaking for constructing with historically-accurate methods and hand stitching.


  • Joni

    May 4, 2020 at 2:02 AM

    I have both patterns, but the material I have stashed (Waverly 'Felicite' in the mineral colorway – so pretty!) is probably not enough to make the full robe anglaise. I was thinking about making a pet en l'air instead, could I do that easily with this pattern?

    • Lauren Stowell

      May 4, 2020 at 5:26 PM

      Yes you can absolutely use this pattern to make a pet en l'air. In fact, Chrissie did exactly that and it turned out beautifully. I also used the back pleating piece to do the sacque part of my Glasgown polonaise sacque jacket. It works a treat!

  • Kelley Thomas

    August 18, 2022 at 6:26 PM

    Thank you so much. I couldn’t understand why my RALF looked different. I needed to angle those front pieces. I had to take the trim off but I was able to fix it (thanks to you). So annoying that the Simplicity pattern doesn’t address this and when the book was talking about the gore being made into one piece, I had no idea what the heck they meant. Thank you for clearing that up. I am five foot 2 so the hem was fine on mine but dang you musta been mad. I think they should’ve explained this better… alas, my dress will be done for the ball(s) we are attending over the next 8 months. I am so happy. Again, you’ve been a great resource and I thank you so much. Your dress came out beautiful and I love the video with you getting ready. I loved the music you used and it made me tear up thinking about getting to wear my dress after all those millions of hours of sewing. I used a sewing machine. It would have taken me the rest of my life to sew that dress by hand.

  • Casey

    November 11, 2022 at 5:41 AM

    I just bought both of the simplicity patterns and was hoping for some advise on the apparent sizing discrepancy.
    For the undergarments; under “body measurements” it says that a size 40 inch bust equals a size 18, but under “finished garment measurements” it says that the same 40 inch bust equals a size 10 (and doesn’t mention the finished measurements for the waist). So I’m unsure how to pick a size. Likewise the gown has much the same issue with mismatched measurements, though not as severe. I assume the corset and gown would need similar measurements too.
    Haven’t even opened it and I’m already so confused.

    • Lauren @ American Duchess

      November 14, 2022 at 12:24 PM

      apologies, we have no control over how Simplicity sizes the patterns or what they put on the back of the envelope. My best recommendation is to go by the finished garment measurements (make sure they’re a little larger than your body measurements for dresses, but a little smaller than your body measurements for corsets). It’s well known that the big pattern companies do weird things with way too much ease and that the back of pattern envelope numbers bear little relation to the final garment. It’s a major issue. In general, cut the size you think is closest and make a mockup in cheap muslin.

  • Jennifer B

    December 13, 2022 at 3:47 PM

    I’ve had this in my stash for a while, (3, actually bc i Kept forgetting that I bought it *lol*), and am finally ready to make it next year. Curious if you can help with some of the yardage needed: I know these dresses require significant yardage, but how much yardage does the ruffled trim and full petticoat take (if one only wanted the center front panel to be of a fancier stuff)?

  • Jess

    December 23, 2022 at 10:11 PM

    This is very helpful, and so was the reply to Casey! A further question – I have this pattern and the JP Ryan pattern but have made a lovely period appropriate set of undergarments already (using different patterns).

    When taking measurements to determine my size should I wear my undergarments and go from those measurements or go natural?

    • Lauren @ American Duchess

      December 27, 2022 at 11:35 AM

      Hiya – it’s best to take your measurements with your stays on, but do take note that the Simplicity pattern measurements on the back of the pattern can be way off because they add ease. Cut the size that is closest but definitely make a mockup first and adjust the muslin over your stays and underpinnings.

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