DIY griddle - mild steel question

[brett_j]

I just procured a 1/4" sheet (18" x 19") of hot rolled mild steel to be used as a griddle on the firebox of my Klose offset smoker. I had a machine shop in the area cut it to size from a scrap piece of new stock they had laying around. Got it for free as I work with a guy who knows the owner. The plan is to use this as a griddle over the open fire on my offset smoker. The Klose has a lid on the firebox and this sheet fits into the grill slot.

My question is about prepping the sheet to make sure its ok to cook on and also seasoned correctly to prevent rust. I plan on going over the sheet with a few rounds of soap and water to remove any grease/oil or metal shavings. I'm reading conflicting things about whether or not the mill scale needs to be removed. Sounds like it can be quite a pain and some folks are saying its just a layer of iron oxide that is ok to leave on there. Anyone here have any expertise in the area and could provide their thoughts?

And as far as seasoning, I'll rub it down with some oil or pam and let it bake for a while to try and establish a protective layer. Would leaving this at the top of the firebox (on the inside of the lid) on a permanent basis be a bad idea? My concern is that it would be directly over the fire and be too hot of an environment to maintain any seasoning built up.

Thanks!

 

[Czarbecue]

I made a second Baking Steel clone by removing the mill scale with a grinder/sander attachment. The steel plate was 3/8” thick and I didn’t want any fragments of mill scale to leave with my pizza or bread.

I seasoned it as I would a cast iron pan. It will eventually turn black if you leave it all day on top of the firebox.

 

[enduro]

If you clean it up good and get it hot enough to remove any impurities that are already in the steel before you put food on it, you should be fine. Depending on how big it is and how much stress is in it, you may experience warping though. If it warps on you, you can straighten it back out and weld bracing along the sides and possibly a "X" brace on the backside in the future.

 

[m-fine]

You will probably not be able to leave it in all the time as your suspicion is likely correct. Too hot will burn off the seasoning and promote rust.

I would sand it smooth, wash it well, heat it up, and then season with a THIN FILM of oil.

 

[Rockinar]

The millscale needs to be removed. If you dont its going to eventually flake off after the metal expands and contracts and will end up in your food. If you dont have tools to remove it, you can remove it with vinegar. Get a container or a box and line it with a trash bag or something. Let it sit in the vinegar for 3 days and hit it with a wire grill brush or any wire brush. It should come off.

Id also remove the plate when not in use. I suspect it would rust if you dont. I made a plate for mine to put in the upper slot on mine to help preserve to top of the firebox. It quickly rusted.

 

[Kmm]

Get rid of the mill scale, if you don't, it will cause you problems for a long time. 18x19 isn't all that big, so you should be able to get it off mechanically. Get ahold of a couple 60 grit aluminum oxide flap sanding disks and go to work. Sometimes it is really stoborn and you will be forced to use an acid bath. Once scale is off, hit the plate with 120 grit and then 220 wet/dry. Remove sanding residue with paper shop towels until towels are clean when you wipe, coat with thin layer of canola oil and repeat shop towel process. Oil again and season as you would cast iron.

 

[brett_j]

Thank you all for the replies. Sounds like trying to remove the mill scale is a good idea. I like the vinegar option as I don’t have a lot of power tools for grinding/sanding.

Thanks again.

 

[thirdeye]

I can't believe the mill scale on 1/4" plate is very heavy (or thick). I would power brush the cooking side of the plate and see what you have. Then a flap disc should remove the scale and give you a nice smooth finish. If you do have some quarter sized pieces, try tapping them with a ball peen hammer. Lightly, you don't want to leave a dent you only want to crack the scale. If it still remains, try a light tap with a chisel.

On plate that thin I'm worried about warping too. What kind of temps do you think the plate will see when it's in use? When it comes to warping or deflection (twist) gradual heat is your friend. Warming it up slowly and cooling it down slowly is best. Can a stiffener or strong back be used, or will that mess up your design?

 

[jpbsarris]

I've made several griddles from 1/4 inch plate and I always remove the mill scale. It can be really tough to get off with a flap wheel. I always use muriatic acid to remove it. Keep it seasoned like cast iron cookware.