FROST AND ICE BUILD-UP ON THE WINGS DUE TO COLD SOAKED FUEL DURING A LAYOVER AFTER THE THOROUGH PREFLT INSPECTION IS MADE. THE DISCOVERY IS MADE BY RAMP PERSONNEL AND DEICING IS ACCOMPLISHED.

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WING ICING DUE TO COLD FUEL BUILT UP MUCH SLOWER THAN EXPECTED. WE ARRIVED EARLY IN MCI (FROM OAK) SO WE HAD A 45 MIN TURN AT THE GATE. ABOUT 25 MINS AFTER ARR; I CHKED THE WINGS. THE BOTTOM OF THE R WING HAD A THIN LAYER OF FROST UNDER THE FUEL TANK AND THE L WING WAS JUST WET. (AS A REMINDER; OUR EXACT LIMITS ARE 'FROST UP TO 1/8 INCH THICK ON THE LOWER WING SURFACES DUE TO COLD FUEL IS PERMISSIBLE' FOR TKOF. FOM LIMITATION SECTION). THE TOPS OF BOTH WINGS WERE CLEAN. HOWEVER; DURING THE NEXT 15 MINS OF THIS UNUSUALLY LONG TURN; ICE CONTINUED TO FORM UNDER THE WINGS AND ON TOP AS WELL. FORTUNATELY; A RAMPER CAME TO THE COCKPIT TO ASK ABOUT THE ICING. IN MY MIND; I HAD CHKED THE WINGS QUITE A WHILE AFTER ARRIVING AT THE GATE -- AND AFTER HAVING BEEN REFUELED -- AND THE WING ICING WAS WITHIN LIMITS TO DEPART WITHOUT DEICING. HAD IT NOT BEEN FOR THE VIGILANCE OF A RAMPER SPURRING ME TO LOOK AGAIN; I MAY NOT HAVE DISCOVERED THE INCREASED ICING. SO BECAUSE THE WING TOP SURFACES HAD SMALL AMOUNTS OF ICE AND THE BOTTOM OF ONE WAS PUSHING THE 1/8 INCH LIMIT; WE DEICED PRIOR TO DEP. I SUBMIT THIS RPT BECAUSE I'M SURPRISED THAT THIS ICE FORMED SO SLOWLY/OR SO LATE. I'VE ASSUMED IN THE PAST THAT FUEL IN THE TRUCK OR HYDRANT SYS WOULD BE MUCH WARMER THAN FREEZING; AND THAT REFUELING A DASH 700 WOULD WARM THE COLD SOAKED FUEL IN THE WING TANKS. AS A RESULT OF THIS EXPERIENCE; I WOULD RECOMMEND CHKING DASH 700 WINGS FOR COLD FUEL INDUCED ICING AS CLOSE AS POSSIBLE TO PUSH TIME.