As you become a more advanced dressmaker, you will find yourself experimenting with more unique fabrics such as embellished laces and silk sheers (to name just a few). While there are a few challenges when sewing with these specialty fabrics, nothing provides more of a test than sewing darts within heavily decorative fabrics.
The process starts with transferring the dart lines from the pattern to fabric, which in itself is a challenge. Heavily decorative fabric like beaded or sequined ones, cannot be marked by conventional means such as fabric pencils or tracing paper. The best way to transfer dart lines is by using tailor tacks to mark key points along each dart line.
For more comfort and precision in the dart stitching process, it helps to replace the tailor tacks with temporary hand basting stitches as they provide an actual line to follow in the construction process. To apply the hand basting, use the tailor tacks as a guide to connect them into straight lines form the dart's vanishing point to each corresponding notch along the seam edge. Once the hand basting is applied, the tacks can be easily removed as they are no longer needed.
Marking the dart lines as precisely as you can will not only help in the sewing process by providing a stitch line, it will also help with an important dart preparation step: Before folding and stitching the dart, remove all decorative elements from within the dart intake only. Doing so will eliminate bulk in the finished dart, will provide flexibility within the folded dart excess, and allow it to lay smooth without causing unwanted bulk in the finished garment.
Depending on the fabric, the decorative elements are carefully removed individually using a seam ripper. As you remove each sequin or beading, be careful not to accidentally catch/pull the fabric surface underneath. Spending a little extra time and care at this stage in the process, will greatly facilitate the dart alignment and stitching later on.
It is important to remove the decorative elements only from within the dart intake and not past the dart lines into the rest of the garment surface. Doing so will ensure that when the dart is stitched, the dart seam blends into the fabric surface, with no interruption/spacing in the placement of the embellished elements.