There are many other forms of improved grate for kitchen stoves, which have nearly superseded the ancient plain or dumping grate, on account of their efficiency, in intelligent hands, in saving coal and labor. With a grate of the Smythe type, if care is taken to turn the bars over once, before any shaking or poking is done, nothing will be removed from the fire-box but the layer of clinkers and thoroughly calcined cinders which collects at the bottom of the fire; and, if the fine ashes are then removed by rocking the grate, without turning the bars over, no unburnt or half-burnt coal need reach the ash-pan, and the dusty and disagreeable labor of sifting out the unburnt coal from the ashes can be dispensed with.

With any grate, care must be taken to remove the ashes from the pan before they accumulate too much. If the heap of ashes and cinders reaches the bottom of the grate, or even approaches very near it, so as to cut off the access of cool air to the under side, a brisk fire is likely to melt portions of the grate-bars, and ruin the grate; and, for a somewhat similar reason, the fine ashes which collect among the coals should be well shaken out before the draughts are opened to quicken the fire; otherwise the increased heat will melt together the loose particles of ashes and form clinkers, which not only adhere obstinately to the fire-brick linings, and to the bars of grates not specially designed for their easy removal, but, by filling up the interstices between the grate-bars, cut off the access of air, and materially check the fire.

Even if the grate is of a good pattern, and the fire is kept clear, the stove may not work well; and the trouble may be due to any one of several causes. The principal one of these is likely to be insufficient draught in the chimney, and this again may have various reasons. It is obvious that a considerable force is necessary to draw the smoke and hot gases from the fire-box through the long journey around the oven; and anything that inconnect the couplings of the water-front with those on the boiler be large, but the upper pipe, which carries the water heated by the fire into the boiler, should rise somewhat sharply from the stove to the boiler. If it rises only slightly, or runs for a part of its course nearly level, as is often the case, the movement of the hot water through it will be sluggish; and, when the current is slow, the water is kept too long exposed to the fire, so that it boils or simmers, or sends large bubbles of steam into the bath-boiler, where they are suddenly condensed, with a thumping or hammering noise, by the colder water there. In either case a great deal of heat is uselessly absorbed in forming steam which, with a better circulation, would serve to heat the water quietly and rapidly, and to keep the upper part of the boiler well filled with a reserve of hot water.

Bad draught terferes with the chimney draught at once affects the working of the stove. Very often, the chimney itself is at fault. The flue may be too small, or choked with fallen bricks, or exposed to down-draughts from neighboring roofs, or buildings, or trees, or hills; and troubles of this sort may be investigated and treated as described in the chapter on Chimneys and Fireplaces; but the draught of kitchen flues is frequently affected in other ways. Where the flue is of good size, not less than eight inches square, or, better, eight by twelve inches, and the chimney rises well above neighboring roofs, and shows no evidence, on being tested, of obstruction, the trouble, if the draught is defective, should be sought inside the house, and will, in most cases, prove to proceed from some leakage of cold air into the flue. It will be remembered that the admission of a very small amount of cold air, to mix with the hot gases in the flue, will chill them so as to reduce materially the draught of the chimney; and there are many ways in which cold air can get into a kitchen flue. A crack in the oven, for example, or imperfect fitting of the removable ovens used in many stoves, or a cracked top, or broken cover, or an open joint in the smoke-pipe, will admit quite enough cold air to affect the draught; and, where no defects of this kind are found, a diligent search will often discover that an ash-pit door, in the cellar or elsewhere, communicating directly or indirectly with the kitchen flue, has been left open, or has been forced open by accumulation of rust; or the mason who built the chimney may, instead of keeping the kitchen flue entirely separate and isolated from top to bottom, have opened it at the lower end into a general ash-pit, through which it can draw air from other flues, or from the ash-dumps of fireplaces. If no other reason can be found for the defective draught, something of this kind may be suspected, an investigation made by taking out a few bricks at the lower end of the flue, and the proper measures taken to shut it off from the ash-pit, if necessary.

Besides the troubles due to these defects or leakages, the draught of kitchen flues is very often injured by using the same flue for another stove, or broiler, or similar apparatus, or for ventilation. It is very common to see the lower end of a kitchen flue, in the basement, used for a laundry stove or a wash-boiler; or a laundry stove, or a broiler, set in the kitchen, beside the kitchen stove, and using the same flue; or a hood may often be seen, placed over the kitchen range, to collect and carry off the smell of cooking, with an outlet into the range-flue; or the same flue may be used for stoves in the chambers, or to receive the local vents, or other ventilation pipes, from bath-rooms or water-closets. In all these cases the draught will be more or less affected. If the kitchen flue is of ample size, and of good height, an air-tight stove may usually be connected with it in the stories above without evil consequences, or a two-inch local vent from a water-closet may safely be carried into it, for the reason that either of these furnishes a comparatively small volume of cold air, and the air which they introduce enters the flue far above the kitchen fire, at a point where the smoke and hot gases from the latter have already received their first impetus, and have begun to cool of themselves, so that a slight addition of cold air produces less effect; but the connection of a large ventilation pipe, or of the smoke-pipe from an open stove, or any admission whatever of air into the flue in or below the kitchen, is very injurious, and, if separate flues cannot be utilized for such supplementary apparatus, they should be shut off entirely, or, if this is impracticable, they should be fitted with tight dampers, to be opened only when the extra apparatus is in use, and in a condition to contribute hot air, instead of cold, to the flue.