When asking are silver and gold liquid investments the answer is going to depend on a few variables. First and foremost will be the relationship, if any, you have built with a dealer or broker. Who's buying the metals? Do they buy in times of rising prices as well as falling?
Another variable is the price you paid for the commodity and the spot price at the time your thinking of selling. An asset is only liquid if you can recoup the initial investment, plus a profit. Anything else is a loss. This would present the argument that selling when you can't earn a financial gain doesn't make any sense.
Usually finding someone to buy the gold is not a problem. Getting the best price you can will take a little research and focus. There are local bullion dealers across the country that will buy your gold at any time. The Internet now provides a multitude of options for trading precious metals, that exposes it globally.
Liquid means you'll be able to sell or "liquidate" the asset at any time that you wish. While this may be true with gold to a certain extent, finding someone to give you the spot price for silver is certainly a little harder.
Liquidity of Silver and Gold: Coins Verses Bars
Coins have the extra appeal as numismatic items and with this sometimes comes an added value, additional to that of the precious metal content. They have the benefit of a global collector base that avidly seek out high grade examples of all coins. Most importantly obsolete certified examples with varying rarities. These coins hold there value for the numismatic value that can only increase with time and the new influx of collectors that have entered the fray via the Internet.
Gold and silver bars are also considered a liquid asset. I again stress the need for a good relationship with your buyer. Most will designate a percentage they will pay, in relation to the spot price and also a sell price that you can buy at. The difference between these two prices is the profit margin the dealer takes. Usually this ends up being a pretty small number.
Some art deco bars carry a premium with collectors as well. These bars and rounds should also be researched before you sell. They may hold a collectible value that far exceeds the precious metal value of the bar.
So to answer the original and rather common question 'Are Silver and Gold Liquid Investments?'. The answer is yes they are. The high demand for these precious metals is expected to continue to rise and a global investor base as well as collector base keeps the prices rising. Taking a profit is as easy as finding the right buyer.