The shift is a women's most intimate garment, worn closest to her body and most often made by herself. Worn during the day under her clothing and at night to sleep in, it is her most laundered article of clothing made with care to withstand this constant use. Made most often of linen for its durability. Linen is stronger when it is wet than cotton. The shifts were cut most economically with little waste of the yardage. Shifts were white, a most practical consideration with their frequent washings. In New England we would be using the England term 'shift' for this garment.
Fabric When making your shift choosing a fabric is your first decision. Linen is a durable fiber that will give you years of use. Today's linen is often more expensive than cotton fabric. This garment by its very nature will show little of itself. A fabric of either material is acceptable. Choosing a light to mid-weight linen or 100% cotton would be a good all round choice for a country women's everyday wear. Finer fabrics would represent one's best or a person of wealth. You will see references to shifts made of muslin when looking at original sources. Eighteenth century muslin was made of flax (linen) and of various qualities, some of which were very fine and desirably sheer.
Patterns Several options for patterns are available for making your own shift but one is not necessary. Beth Gilgun's book, Tidings from the 18th Century gives very clear directions for cutting and constructing your own. Not ready to try one without a pattern? I would suggest the Kannik's Korner shift pattern because of its documentation and clear instruction of the details. It has a fixed neckline, as often the extant garments were. The reenactor has tended to use a drawstring neck opening and it is a convenience for a less exacting fit. You can adapt the neck in this pattern to a drawstring by cutting the neck opening a little larger, turning a 1/2" in seam and drawing a 1/4' tie through it.
Construction details When considering the shift's length it would be wise to keep in mind that this garment is also a night gown and may well be yours if you're a weekend re-enactor. Mid-calf length is a good choice for two reasons. It seems to stay in place and not ride up while worn and it allows for any additional shrinkage after the first washing.
The sleeves generally come to a comfortable length below the elbow. This length, or lack of it, keeps them from sliding down when the ties loosen and out of the way while working. The edge may be a casing with a drawstring or you can add sleeve bands with 'link holes' on either side. You would then use "button-links' as today we think of cuff links, to close the band or each cuff could be tied with a ribbon. Simply attach two buttons together back to back with thread or wire to make you own. The fullness or lack of, in the sleeve is a way to show off your intended social station. The fuller cut and finer fabric showing wealth and higher social standing.
The person you represent might choose to 'fancy up' her better shift with ruffles added to the sleeve edges and/or the neck edge. This would be done using fabric, either self-fabric or a finer fabric. Lace was an imported and expensive item during this period and would be worn generally only by someone representing a women of wealth. A maid servant may have a case for a simple lace if she is seen with her employer, possibly, you'd better have a good story. Lace was more often removed and kept by it's original owner. It would be better to save lace for those events where everyone is upper class and then spend your time trying to find one that is reasonably appropriate.
Sewing Tip: Before cutting your fabric look to see if you have a fine salvage. If so, cut about two inches off the fabric along this selvage edge and use this for your ruffles on shifts or caps as its finished edge will save you hemming time and is most attractive and accurate.