Everyone knows that 2 lb. foam is suppose to have a density of 2 lbs, but what does that really mean, and why should you care?
So what does it really mean:
2 lb foam gets its name because that is the weight of a cubic foot of the end product.
Why should you care:
With the price increases of the last little while, it's important to get the most out of what you pay for. If you are getting an average of 2.0 density foam you are doing extremely well. If you are getting 2.5 or higher, you are making next to nothing.
Let's look at some facts to back this up. An average set of material 1000lbs (500 of each material). When the chemical reaction happens, it is impossible for extra weight to be added. However it is possible for the total weight to be reduced (steam has to account for something). This loss is so small that this math will not account for it.
If you sprayed every drop of the material you will have 1000lbs of material sprayed out. If this 1000lbs was sprayed out at 2lbs per cubic foot, you will get 6000 board feet from the set.
If you spray a every drop of material at 2.5 lb. density, you will get 4800 board feet from a set.
If you want to see the math for this (this is where stupid algebra can make you money) follow this line of thinking. We know that " a cubic foot = our density " right? So that means 12 board feet equals our density.
The next step is to find out how many board feet 1 lb. of material equals. To do this we divide 12 by our density (BF / D = 1 lb. after we figure this out, all we need to do is multiple that number by 1000 and we will learn what the board footage of our set is.
Now that you have seen read it in words, let's see it in numbers.
Let's start with the formula:
(BF / D) * LBS = ?
BF = 12 = number of board feet in a cubic foot
LBS = 1000 = lbs of material in a complete set
D = your density
? = Is the board feet from your set
Now let's plug in some numbers:
we will use a density of 2...
(6)*1000 = 6000
So with an average density of 2 we will have a board footage of 6000.
We will use a density of 2.5
(12/2.5)*1000 = ?
(4.8)*1000 = ?
(4.8)*1000 = 4800
So with an average density of 2.5 we will have a board footage of 4800.
Now that you see how the math works you can see that if your average density is off by .5lbs per cubic foot, you can either loose or gain an extra $1200 per set!!
In the summer time most people use a board footage number of around 4500 per set, when quoting jobs. Using a number like this will have a density of 2.66. Knowing how to control your density and how to predict what you will get from each set, will help you quote the tighter on the jobs which you really want, or it can just increase your profit margins! Both of which are great things for you.
If you are having a hard time getting at least 2.3 -2.5 density on average, you should look at how you are spraying. There are many things you can try to tweak your systems and get the most out of your material.