It really depends on what sort of piece it is. Typically if it's a frame or soemthing decorative, it's its necessary. That said, I always too coat to bring out the depth of color, especially in flat sheen paints. Please feel free to message me if you have any more questions.
@Simple Southern Charm The piece is an armoire that I am going to use for storage in my office. I was wondering if I needed to protect it with the poly because I will be putting pictures on top of the armoire.
I would definitely use a top coat.
I use water base polyurthene or wax. On tops always poly, but many people have wonderful results with wax.
You didn't say what type of paint you plan to use. That can make a difference.
If you are using latex paint, a top coat is optional. When using latex paint (my preferred paint), I do not top coat the furniture I paint for my home simply because the top coat products I have tried in the past generally change or discolor the paint color somewhat--even the "non-yellowing" products. I want my colors to stay true, especially pure white. Also, we are not particularly hard on our furniture so it doesn't get chipped or dinged very much, if at all. If something does get a ding, I can easily take a brush and a dab of paint and do a touch-up.
The thing you need to be aware of with latex paint is, depending on the weather, it can take up to 30 days for latex to completely cure and while the piece will be dry to the touch long before then, I would hesitate to lay anything on the shelves or top until you are absolutely sure it has completely cured. Otherwise, papers, books, frames etc. can stick and pull your paint off when you go to remove them.
If you are going to distress the piece anyway, I don't know if I would bother with a top coat. Any additional wear to the paint will just look that much more authentic.
If you are using chalk paint or milk paint, yes, you will need to use some type of protective finish. It can be wax or a top coat like poly. In addition to protecting the paint, wax or poly will give the very flat, matte finish of chalk paint and milk paint some luster. The Miss Mustard Seed Milk Paint line of products also offers a Hemp Oil that can be used as a protective finish over milk paint (and I've used it over chalk paint, as well). You just wipe it on, let it sit for a little bit and wipe away any excess that is not absorbed. No buffing required like with wax.
I would use a satin finish of ploy. It will protect without a shine and will dust off easier as well.
I agree with Linda - use a satin poly. You will love the look and dust wipes off easily. Good luck. Please post the finished product.
It just depends on what type of paint you use and how much the piece will be used. You didn't say what product you used for your paint?
Some people paint their piece with chalk paint or milk paint, distress it, then protect it with soft wax intended for use over chalk paint. You can use a clear wax, or a dark wax, then buff it off. The dark wax is often applied over clear wax to give your piece a slightly darker color which 'ages' it and is considered an 'antiquing' look.Look for more about this on Hometalk or pinterest. Examples of this are on etsy also.
I use a product called block it by vintage market and design furniture paint!
if you used chalk paint and want the shabby chic look use clear wax. If your really going to beat it up use poly but use the matt finish. It is a little harder to find but worth the effort.