Tuesday, April 20, 2010

Exodus 27:6-8 - The Copper-plated Staves of the Altar of Burnt Offering

Just like the rest of the furniture of the Mishkan, the Altar of Burnt Offering would have Staves made for it to allow to transport it around. Lets' take a look:

Exodus 27:6-8
6 And thou shalt make staves for the altar, staves of shittim wood, and overlay them with brass.
‎6 ‏וְעָשִׂ֤יתָ בַדִּים֙ לַמִּזְבֵּ֔חַ בַּדֵּ֖י עֲצֵ֣י שִׁטִּ֑ים וְצִפִּיתָ֥ אֹתָ֖ם נְחֹֽשֶׁת׃
Just like the Staves of the Ark and the Table, the Staves of the Altar were made out of Shittim wood. There were two Staves made for the Altar. The most probable length of the Staves would be in the range of 10-15 cubits, 3-5cm in diameter(a hand-grip diameter). Since I'm not yet sure how the length of the Staves was calculated, I'm just going to assume at this time that the Staves were 11 cubits long.

The Staves were overlayed with Copper to match the Altar material and to provide extra strength to the Staves.

7 And the staves shall be put into the rings, and the staves shall be upon the two sides of the altar, to bear it.
‎7 ‏וְהוּבָ֥א אֶת־בַּדָּ֖יו בַּטַּבָּעֹ֑ת וְהָי֣וּ הַבַּדִּ֗ים עַל־שְׁתֵּ֛י צַלְעֹ֥ת הַמִּזְבֵּ֖חַ בִּשְׂאֵ֥ת אֹתֽוֹ׃

The Staves were put into the rings like so...

And now, the Altar could have been comfortably carried around on the shoulders of four men.

As I have mentioned in my previous post, I'm still trying to establish the exact position of the rings of Altar.
As you can see from the image above, if the Rings were positioned three(3) cubits off the ground, then it would leave approximately half a cubit(0.5) of space between the ground and the Altar, when carried.
On the other hand, if you the Rings were positioned, say two(2) cubits of the ground, it would then leave approximately one and a half (1.5) cubits of space between the ground and the Altar, when carried.
You can see the result of this alternative positioning of the Rings on the picture below.

The last verse of the description that deals with the Altar of Burnt Offering is Exodus 27:8.

8 Hollow with boards shalt thou make it: as it was shewed thee in the mount, so shall they make it
‎8 ‏נְב֥וּב לֻחֹ֖ת תַּעֲשֶׂ֣ה אֹת֑וֹ כַּאֲשֶׁ֨ר הֶרְאָ֥ה אֹתְךָ֛ בָּהָ֖ר כֵּ֥ן יַעֲשֽׂוּ׃ ס

If you remember, the Altar and its four horns (not the Grate) were made out of Shittim wood overlayed with Copper (Ex.27:1). Like this:

This is very important detail, because there was a good reason: to reduce weight of the Altar.

If we assume that the density of Shittim wood was 780 kg/m³ and the one(1) cubit was equal to 0.45m, then the weight of:
  • The Copper plated Altar would be [[(5cu*0.0225cu*3cu)*0.45^3]*4sides]*780 kg/m³  = 95kg+ negligible weight of Copper plating = ~100kg.
  • The Solid Copper Altar would be [[(5cu*0.0225cu*3cu)*0.45^3]*4sides]*8930 kg/m³ = 1098kg!!!
To put these numbers in perspective, an altar made of solid copper alone would weigh about a ton, and would require at least 16 people(or more) to carry it.

So, as you can see, this little detail in Exodus 27:8 plays a huge role in understanding the design of the Altar of Burnt Offering.

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