I spray baste with 505 and have never had any problems and I always iron my sandwich, front, then back to ensure there are no excess folds of fabric from layering and to also set the spray as mentioned by someone else. For a small project like a placemat, I may spray in my house if the weather is not conducive to outdoor spraying, placing the item on an old sheet to protect carpet, etc from overspray, but on larger items I always take the top and the backing outside and hang them one at a time on either the clothes line, or over my deck railing (which I cover with the old sheet) do my spraying, then bring the pieces inside to put into the sandwich. The spray is temporary, and can be repositioned, so it works quite well to do the spraying outdoors, fold it up and bring it in for sandwiching. After a few uses, I'll throw the sheet through a regular wash and it removes the spray, which might take twice if there is a build up from doing several quilts. I've done every quilt size including several kings, and it works great, without any problems with my machines.