Cold ash = easy fire?

[spot]

I have an open wood burning fireplace.
No insert, no wood stove.
It doesn't make much heat, but it sure looks pretty.
I like it.

I have noticed that if I don't clean the old ashes out from under the log grate...the next fire lights easier, stays lit, and gets "rolling" sooner.
This is even if there are no hot coals to help...as my fires can sometimes be several days apart.

When I do clean the ashes out - I find that I sometimes have to fight to get the next fire going. The wood just doesn't want to cooperate if there isn't any previous ash.

Why is this? Is it an airflow issue? Does the layer (1-1.5 inch) of ash act as a damper to "choke" the fire into burning? Does even cold ash help with combustion?

 

[danielj618]

I have an open wood burning fireplace.
No insert, no wood stove.
It doesn't make much heat, but it sure looks pretty.
I like it.

I have noticed that if I don't clean the old ashes out from under the log grate...the next fire lights easier, stays lit, and gets "rolling" sooner.
This is even if there are no hot coals to help...as my fires can sometimes be several days apart.

When I do clean the ashes out - I find that I sometimes have to fight to get the next fire going. The wood just doesn't want to cooperate if there isn't any previous ash.

Why is this? Is it an airflow issue? Does the layer (1-1.5 inch) of ash act as a damper to "choke" the fire into burning? Does even cold ash help with combustion?

I would think that you have some charcoal chunks..(black chunks of wood that have not burnt down to ash yet)..in my experience when I have some of it left over in my woodstove..I pile it in the middle and build my kindling over it..I get rid of most of the ash but those chunks get red hot quick and you have a quick bed of coals

thats what I am thinking

 

[DiscoInferno]

I think it's because the ash insulates the fire from the cold fireplace floor, and thus helps keep the new fire hot. I'm not sure why that would be a major difference when using an elevated grate, though.

 

[Gooserider]

I have an open wood burning fireplace.
No insert, no wood stove.
It doesn't make much heat, but it sure looks pretty.
I like it.

I have noticed that if I don't clean the old ashes out from under the log grate...the next fire lights easier, stays lit, and gets "rolling" sooner.
This is even if there are no hot coals to help...as my fires can sometimes be several days apart.

When I do clean the ashes out - I find that I sometimes have to fight to get the next fire going. The wood just doesn't want to cooperate if there isn't any previous ash.

Why is this? Is it an airflow issue? Does the layer (1-1.5 inch) of ash act as a damper to "choke" the fire into burning? Does even cold ash help with combustion?

I suspect that it is a combination of airflow and the fact that ash is a pretty decent insulator that will serve to keep the hearth material from sucking to much heat out of the fire. (Remember that heat is one of the essential parts of a fire, if you have lots of cold airflow or hearth material cooling your fuel it might be very hard to get it going.)

Gooserider

 

[kd460]

I have read here before that a fire box with some leftover ash in it does burn better than a clean one. Don't know why, but, seems like you have confirmed that. he previous explanations sound like good ones. KD

 

[Corey]

I know there is an old chemistry demonstration of trying to burn a plain sugar cube (which won't) then rub some ash on it and try again (this time it will light right up). So ash can act as a catalyst to aid burning in certain situations. I don't know the exact mechanism - I have seen it attributed to everything from trace amounts of metals, carbon, even thorium in the ash.

I wonder if it would work even better to actually rub some ash on the logs? Never seen that done before!

Corey