It never fails, right? You finish a craft project only to find the beginnings of fraying and frizzing at the ends of ribbons and threads. You have to find some way to prevent these from continuing to fray, and even better would be to find a way to fix the current fraying. You have many options, some of which are washer-friendly, too.
Heat Sealing With a Lighter, Match, or Candle Flame
If the ribbon is made of a material like nylon, the ends should melt rather easily if you hold them up to a flame, such as from a candle or match. If done correctly, the edges should quickly melt and form a raised edge. The material does need to be one that will melt, and it would be better if the edges of the ribbon weren't going to be front and center because the melting can look a bit unkempt. You also have to be able to melt the ends of the ribbon when they are not right next to the rest of the material in your project. If you've sewn the ribbon onto a bag, for example, and you have to hold the heat source close to the bag, you could end up melting the bag. But if you have a few inches of clearance around the ends of the ribbon, you should be OK.
Hold the ribbon end in one hand. Either place the flame source on a stable surface (for candles) or hold the flame source in your other hand, and put both elbows on a table. That will stabilize your arms. Moving relatively slowly at this point, move the ribbon end toward the flame. The second you see the ends start to congeal, move the ribbon so that the entire end is exposed to enough heat to cause the end to melt and congeal. This happens very quickly, so do not take your eyes off the ribbon. Let the ribbon end cool for a few minutes.
Commercial Sealers, Craft Glue, and Clear Nail Polish
You can also use substances like craft glue, clear nail polish, and commercially available sealants to seal the ends. Brush glue or polish on the ends or dip the ends in the sealant. Do this in a well-ventilated room. Let dry for several hours. This is best for materials that aren't going to go through a washer and dryer. While some craft glues and sealants are washer-resistant, the agitation can still shake parts of the ribbon ends loose.
Sewing or Serging
One option that can take longer but have less smelly effects -- and that is washer-friendly -- is to sew the ends of the ribbon securely. You can do this by hand if you want. If you have a serger, make a few practice runs in scrap cloth so that you know how fast the serger will go once you try to fix the ribbon ends.
It helps to know the composition of the ribbon, too, when choosing an anti-fraying method. (You don't want to try melting cotton, because it won't work.) Double-check with the customer service people for the ribbon companies you buy from to see what materials are in use and if there are additional ways to stop fraying that the employees know about. Contact a company like Wholesale Flowers Ribbons & Buttons for more info.