<div style="margin: 12px 0px; font-family: arial; color: #333333; background: #ffffff; border: solid 4px #e5e5e5; width: 100%; clear: left;"><div class="CM_CTB_Content_Wrap" style="margin: 0px; padding: 0px;background-color: #ffffff;"><div style="border-bottom: solid 1px #dcdcdc; white-space: nowrap; margin-bottom: 8px; background-color: #eeeeee ;background-image: url(http://clipmarks.com/images/source-bg.gif); background-repeat: repeat-x; height: 24px; line-height: 24px; vertical-align: middle; padding-bottom: 4px; color: #666666; font-size: 10px;" ><a href="http://clipmarks.com/clip-to-blog/" title="see clips that are hot right now"><img src="http://content.clipmarks.com/blog_embed/0ed27ff0-64eb-40b2-a584-c14dde5b97a6/5B2B1F26-1E89-4E87-B910-31ED0E6715ED/" alt="" width="19" height="19" border="0" style="vertical-align: middle; margin: 0px 4px; display: inline; border: none; float:none;" /></a>clipped from <a title="http://www.britannica.com/EBchecked/topic/268403/hoarfrost" href="http://www.britannica.com/EBchecked/topic/268403/hoarfrost" style="font-size: 11px;">www.britannica.com</a></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.britannica.com/EBchecked/topic/268403/hoarfrost"><P> <SPAN class="bps-assembly-container bps-assembly-left bps-mag"><A href="http://www.britannica.com/EBchecked/topic-art/268403/118048/Hoarfrost" class="bps-assembly-image"><SPAN class="bps-mg"></SPAN><IMG height="67" width="100" ieheight="67" iewidth="100" src="http://media-2.web.britannica.com//eb-media/63/123863-003-509FD99A.gif" title="Hoarfrost. [Credits : Daniel Schwen]" alt="Hoarfrost. [Credits : Daniel Schwen]" class="bps-asset-img" /></A></SPAN> deposit of <A title="ice crystals" href="http://www.britannica.com/EBchecked/topic/839845/ice-crystal" class="bps-event-selector bps-topic-link"><SPAN>ice crystals</SPAN></A> on objects exposed to the free air, such as grass blades, tree branches, or leaves. It is formed by direct condensation of <A title="water vapour" href="http://www.britannica.com/EBchecked/topic/637333/water-vapor" class="bps-event-selector bps-topic-link"><SPAN>water vapour</SPAN></A> to ice at temperatures below freezing and occurs when air is brought to its <A title="frost point" href="http://www.britannica.com/EBchecked/topic/220910/frost-point" class="bps-event-selector bps-topic-link"><SPAN>frost point</SPAN></A> by cooling. Hoarfrost is formed by a process analogous to that by which dew is formed on similar objects, except that, in the case of dew, the saturation point of the <A title="air mass" href="http://www.britannica.com/EBchecked/topic/10749/air-mass" class="bps-event-selector bps-topic-link"><SPAN>air mass</SPAN></A> is above freezing. The occurrence of temperatures below 0° C (32° F) is not enough to guarantee the formation of hoarfrost. Additionally, the air must be initially damp enough so that when cooled it reaches saturation, and any additional cooling will cause condensation to occur. In the absence of sufficient moisture, hoarfrost does not form, but the water in the tissues of plants may freeze, producing the condition known as <A class="bps-ref-anchor" id="ref3337" name="ref3337"><SPAN></SPAN></A><A title="black frost" href="http://www.britannica.com/EBchecked/topic/67860/black-frost" class="bps-event-selector bps-topic-link"><SPAN>black frost</SPAN></A>.</P></blockquote></div><div style="margin: 0px 6px 6px 4px;"><table style="font-size: 11px;border-spacing: 0px;padding: 0px;" cellpadding="0" cellspacing="0" width="100%"><tr><td style="background:transparent;border-width:0px;padding:0px;">&nbsp;</td><td align="right" style="background:transparent;border-width:0px;padding:0px;width:107px" width="107"><a href="http://clipmarks.com/share/5B2B1F26-1E89-4E87-B910-31ED0E6715ED/blog/" title="blog or email this clip"><img src="http://content9.clipmarks.com/images/c2b-foot.png" border="0" alt="blog it" width="107" height="17" style="border-width:0px;padding:0px;margin:0px;" /></a></td></tr></table></div></div>

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