Method of imparting color to fires

An improved method of imparting colors to fires in home fireplaces is described as well as the preparation of the materials used to provide said color. Metal salts which impart color to flames are granulated using hydrated alkali metal silicate as a binder. When these granules are added to fires, the silicate binder softens on contact with warm or hot combustible material. The silicate then loses water and is transformed to a solid once more so that the material becomes bonded to the combustibles. Upon burning the metal salts are decomposed and the flames are colored. The system is very efficient and proper application requires the use of bulking agents in the granules.

BACKGROUND 
This invention relates to an improved method of adding metals salts to 
wood, coal, charcoal or paper fires commonly built in home fireplaces. 
Interesting and pleasing color effects can be produced by the introduction 
of certain metal salts into fires usually built in home fireplaces. 
Presently such materials are dry blends of the various components and as 
such, have certain disadvantages. These blends are non-homogeneous, 
consisting of various particle sizes and shapes. These conditions lead to 
segregation of the powder during storage, handling and especially 
application. In addition the finer particles contained in these blends 
tend to become entrained in the combustion gases exiting the fireplace 
thereby losing their value while contributing to air pollution. Additional 
material can be lost because these powders do not adhere to the 
combustibles and a significant proportion fall to the bottom of the 
fireplace and are not utilized. 
SUMMARY OF THE INVENTION 
An improved method of forming colored flames in fires built in home 
fireplaces involves the addition of granules containing colorants bound or 
agglomerated with hydrated alkali metal silicate. Upon contact with warm 
or hot logs or other combustible materials, the hydrated alkali metal 
silicate softens or melts. The heat causes the loss of water so that the 
silicate rehardens and the composition is bonded to the combustibles. As 
the fire burns thereby consuming the wood and such, the coloring agents 
are decomposed imparting color to the flame. The granules containing the 
colorants are prepared by providing a mass of the desired metal silicate, 
and drying to obtain the desired moisture content. 
The efficient nature of this method of adding colorants to fires requires 
that bulking agents be added to the composition. The addition of such 
relatively inert agents is required to obtain distribution of the granules 
throughout a significant portion of the fire. 
THE INVENTION 
The coloring agents, alkali metal silicate binder and generally inert 
bulking agents, comprise the granules used to impart color to flames 
according to the method of my invention. The salts of any metal that 
provides the desired color can be added to the granules. Among others, 
metals that provide colorful flames include antimony, arsenic, boron, 
chromium, calcium, copper, lithium, lead, potassium, manganese, nickel, 
selenium, strontium, thallium, and zinc. I prefer to use antimony, boron, 
chromium, copper, calcium, lithium, potassium, manganese, nickel and zinc 
as these metals are the most environmentally acceptable. Among others the 
salts of these metals that can be used include sulfate, phosphate, 
carbonate, acetate, oxalates and formates. I prefer to use carbonates, 
acetates, oxalates and formates since these compounds decompose into 
CO.sub.2 and water vapor. I especially prefer to use carbonates for 
economic reasons. Large amounts of sodium and barium salts should not be 
used since the flame colors developed by these metals tend to mask other 
flame colors. 
While the granules used in the method of my invention can be prepared with 
any alkali metal silicate as the binder, sodium interferes with the 
development of other flame colors and is of limited usefulness. Potassium 
and lithium silicates are quite suitable for the binder since both metals 
provide colorful flames (violet and crimson respectively) and do not mask 
other colors. I prefer to use potassium silicate. 
The preferred preparation of the granules according to the method of my 
invention requires that the granules contain a bulking agent. Compositions 
of this type are applied directly on the fire. Application is accomplished 
by tossing a handful, spoonful or capful of material directly onto or into 
the ignited fire. If no bulking agent were added to the granules used in 
my method, the amount required to impart the desired colors would be very 
small and this amount would be less easily applied by these methods. The 
bulking agents should be relatively inert and should not interfere with 
the other functions that are required in my method. Common bulking agents 
such as sodium sulfate and sodium carbonate are unsuitable for this 
application. I have found that sand and other forms of relatively pure 
amorphous or microcrystalline silica are the most useful bulking agents. 
The granules are prepared by admixing 10 to 25 pbw of the desired metal 
salt(s) with 35 to 82 pbw of the bulking agent until it is uniform. 
Sufficient potassium or lithium silicate solution to provide 8 to 40 pbw 
of silicate solids is added and blended with this composition. The 
blending is continued until uniform granules develop. This material is 
dried in any suitable manner to provide apparently dry granules of 
sufficient strength. A heated rotating drum that provides a tumbling 
action is desirable for this purpose. The extent to which the material is 
dried is of critical importance to the method of my invention. If the 
material is over-dried, it will not melt quickly enough to adhere to the 
combustible material. A composition with too much moisture will cake in 
the container and will be almost useless. I have found that between 8 and 
27% water is useful but that 9 to 17% provides a product with the most 
desirable properties. 
The silicate solutions used in this preparation have about 1 to 5 mols of 
SiO.sub.2 per mol of K.sub.2 O or about 2 to 12 mols of SiO.sub.2 per mol 
of Li.sub.2 O. The potassium silicates contain 15 to 40% silicate solids 
while the lithium silicates have 15 to 35% silicate solids. 
The product of this preparation and the material employed in my method of 
coloring flames contains 7.3 to 23% by weight of metal salt(s), 6.5 to 37% 
by weight silicate solids as the binder, 24 to 75% by weight of bulking 
agent and 8 to 25% by weight of water. 
Generally fires that are prepared with materials such as wood or paper burn 
with a predominately yellow flame. The color of such flames can be altered 
by the addition of granules according to my invention containing one or 
more metal salts. Blues, pale blues, greens and pale greens are prevalent 
flame colors produced by such metals as antimony, arsenic, boron, copper, 
lead and nickel. Red of crimson flames can be produced using calcium or 
lithium salts while potassium salts yield violet flames.

EXAMPLES 
The following examples are illustrative of certain embodiments of my 
invention and should not be considered restrictive. The scope and limits 
of my invention are clearly recited in the claims. All proportions are in 
parts-by-weight (pbw) unless otherwise indicated. 
EXAMPLE 1 
Color producing granules for fires were prepared as follows. Copper 
sulfate, nickel carbonate and calcium carbonate (6 pbw each) were blended 
with 55 pbw of fine sand. Blending was continued until a uniform mixture 
was obtained. Then 54 pbw of a solution containing 15 pbw of potassium 
silicate with a mol ratio of 3.3 SiO.sub.2 /l K.sub.2 O was blended with 
the uniform mixture until damp granules were formed. These granules were 
charged to a rotary dryer and dried at 95.degree. C. until a moisture 
content of 12% was obtained. This product was a free flowing, non-caking 
granular powder of uniform composition and particle size. 
These granules were used to color a wood fire in a home fireplace by 
tossing 25 to 50 grams onto the burning wood at various intervals. The 
granules could be seen to melt and then to bond onto the surface of the 
wood. Very few of the granules fell to the bottom of the fireplace and no 
particles could be seen exiting with the combustion gases. The 
predominately yellow flame changed to green, then red with occasional 
flashes of violet. 
EXAMPLE 2 
Lithium acetate (12 pbw) was blended with 61 pbw of sand. Blending was 
continued until a uniform mixture was obtained. Then 54 pbw of a solution 
containing 15 pbw of lithium silicate with a mol ratio of 4.5 SiO.sub.2 /l 
LiO.sub.2 O was blended with the uniform mixture until damp granules were 
formed. These granules were charged to a rotary dryer and dried at 
70.degree. C. until a moisture content of 15% was obtained. This product 
was a free-flowing, non-caking granular powder of uniform composition and 
particle size. 
These granules were used to color a wood fire in a home fireplace by 
tossing 35 to 55 grams onto the burning logs. The behavior and attributes 
of the product were the same as described in Example 1 except that the 
colored flames were crimson.