Coated or Uncoated

We have loads of customers asking us to decide for them whether or not to use uncoated or uncoated papers. Coated and uncoated paper stocks are easily distinguished by their appearance. A coated paper has a shimmer to its surfaces and will feel smooth and waxy to the touch, whereas uncoated papers appear matt and will feel rougher or grainier to the touch. Deciding which type and finish of paper to use for a print job is very important and can drastically affect the way a printed ink appears.
As the name suggests, coated paper has a coating, usually of china clay, which gives it a smooth finish. Coated papers are available in a gloss, silk (sometimes called satin) or matt finish and are used for projects requiring a fine finish, which is why coated paper is sometimes referred to as 'art' paper. Most of the leaflets you get through your letterbox, the glossy brochures you pick up from the travel agent and the fancy programmes you buy at concerts are printed onto coated paper.
Uncoated paper doesn't have a coating and is therefore not as smooth as coated paper. You will use uncoated paper in your laser printer and photocopier. Premium quality uncoated papers are used for business stationery and are becoming increasingly popular for use in prestigious brochures and catalogues as an alternative to the more commonly used coated papers. Uncoated papers are available in a range of finishes.
If you're creating a full colour document featuring photographs or colourful illustrations, you'll get the most vibrant colours if you opt for a coated paper. Whether you choose a gloss, silk or matt finish is mostly down to your personal preference, although gloss paper will produce the most vibrant colour reproduction. Some people think that gloss is classy, others consider it to be a bit tacky. Something to consider if your document is being printed conventionally is that silk and matt papers should normally be machine sealed (a sealant is applied to the printed image to avoid it being smudged). This may add to the cost of printing - check with your print contractor. Uncoated paper can be used for full colour projects but colours tend to be less vibrant and unless you use a low quality bond paper, it could end up costing considerably more than if you'd selected a coated stock.

http://www.tomtheprinter.co.uk/2007/01/choosing-paper-for-your-print-project.html