Most people do not consider a wedding gown to be a "wash and wear" type of garment, particularly considering how expensive most gowns can be. But if you are planning to wear a second-hand gown and it is in need of cleaning, you have many options. You can pay to have it dry-cleaned, which can be an outrageous expense, or you can try to wash it yourself at home.
Remove any exterior attachments from the gown such as detachable bows and trains. These you can put into the washer along with the gown, but keep them separate from the main garment since you do not want them to catch on the washer's paddles and tear the fabric of your gown. Assuming that your gown is second-hand and came to you dirty, you will definitely need to wash it or dry clean it. Washing it yourself is a lot cheaper.
Turn the entire gown inside-out so that when you put it into the washer the beads and sequins do not bounce against the interior of the washer and possibly break off from the garment. Even if there are no beads and sequins you should still turn the gown inside-out to protect any delicate lace from getting torn during the tumbling action inside the washer and to prevent any discolouration of the exterior of the gown. If discolouration occurs from contact with dirt you will always find inside a washer, it is much better that it should be on the inside of the dress where it is not visible.
Set the washer to the delicate cycle and use cold water only. This is a shorter cycle, which keeps the delicate fabrics from tossing too much and risking potential damage. If you use hot water you will run the risk of having your gown shrink, which would be a very unpleasant surprise when you are ready to wear it for your own wedding.
Roll up the gown the best you can and stuff the entire thing into the washer. Don't worry about rolling a bulky wedding gown, it can be done. Just grit your teeth and do it, as the gown can take it. There will be some wrinkling when the gown comes out of the washer, but this is minor and can be repaired later by the use of a fabric steamer.
Remove the gown when the cycle is finished and hang it on a clothesline. If it is raining or in cold weather, you will have to hang it up indoors, but it is much better to hang the gown rather than trying to dry it in the dryer. The dryer will heat up the garment , which may damage delicate fabrics.
Wedding gowns can also be washed by hand, but this takes much longer and requires a lot more effort, especially when you are dealing with yards and yards of heavy satin fabric. However you choose to do it, always use cold water and no bleach.
If the gown comes out wrinkled you may want to try ironing it. Be very careful because the fabric is easily damaged by excessive heat. Using a portable steamer is actually better for the gown, but if you do not own one, and you must use an iron, use the lowest possible heat setting.