Jump to content
I Forge Iron

kast-o-lite 30 LI very weak


Recommended Posts

Hi! I've been lurking around these forums for a while now but just decided today to create an account so I can be involved more in the blacksmithing community.

Anyways, I have a question about kast-o-lite 30 LI. Just yesterday, I mixed some up with just enough water for the refractory to hold its own shape without slumping over. However, after I let it cure for 24 hours, with a damp towel over it, fire cured it, then tested its bending strength, it just broke in half with little effort. It felt soft like a fresh baked sugar cookie that sat out for about half a day. Is that normal? The refractory was molded into a 6x6" 1/4" thick wafer when I tested it. Also, the refractory itself arrived at my house about 4 days ago and Ive been keeping it in my garage.

 

If it is normal, should I mix in some Veegum T or Bentonite to add strength?

Link to comment
Share on other sites

First of all, welcome to IFI!

It sounds like you used to much water in your initial mix; Kastolite takes a lot less water than one might think. I don’t have the figures in front of me, but I almost always mix it by weight to avoid this same problem.

Link to comment
Share on other sites

Officially, one pound of dry Kastolite gets 2.75 ounces of water. I weigh out the KOL and spread it out in a shallow plastic tray first. Then I weigh out the water and sprinkle it lightly over the entire surface. Then I chop it all together with a trowel until every part looks like every other part. It will still look extremely crumbly, but it should hold together nicely once it's packed into place.

Link to comment
Share on other sites

You didn't mention the material of your mold form. In my experience anything that can wick moisture away from the kastolite when you apply it can result in a "crumbly" casting.  Any surface in direct contact with the kastolite should be damp/wet first.

Link to comment
Share on other sites

LeeJustice: Same thing. One fluid ounce of water weighs one Imperial ounce. "A pint's a pound the whole world 'round."

Buzzkill: Or made from/covered with something impermeable. I've lined molds with plastic wrap, with decent success. 

Link to comment
Share on other sites

Welcome aboard Bootlegin, glad to have you. If you'll put your general location in the header you'll have a better chance of hooking up with experienced members living within visiting distance.

The most common water to Kastolite ratio I've seen in too  many headache inducing hours of searching  for instructions from the manufacturer is, "18% water to Kastolite by weight." I've seen ratios as low as 14% but I think those were for gunnite applications.

When you're curing Kastolite after the hard set, 24hrs with a moist surface is recommended most often though it seems everybody just links the same page. Once set it can't be too wet, a moist surface means WET I've cured it in a closed tote, laying in several gallon of water and rolled it over a couple times over the next few days.

It's hard to mix, the aggregate is crushed and angular aggregate keys together making it hard to compact, even aggressive vibration isn't aggressive enough. I found it responds well to being cut together as John suggested, I've had good results kneading it and cutting it. Then I hammered it into my forms with a wood mallet. Troweling it into a form isn't compacted enough, it'll be weak. You don't need to hammer it hard but it responds well, I used a piece of rod to hammer it in my forge.

Another method is to roll it to thickness and wrap it around a form. This is often done for stove parts. If you want 1/2" thick use 1/2" height blocks, rod, etc. to prevent the roller from over thinning. I clamped sq. steel stock to the table at the width I needed and rolled it to a mark, trimming the excess. I'd laid canvas on the table and rolled on it after wetting the canvas. 

Once it began setting I turned it onto a piece of plywood covered in Saran Wrap so the canvas could be removed.

Kastolite sticks to just about anything I've let it touch, I grease forms with old Crisco shortning, even Saran Wrap gets hopelessly stuck but it burns right off when you heat cure it.

Frosty The Lucky.

Link to comment
Share on other sites

Thanks everyone for the excellent advice and warm welcomes! The new test piece just finished curing and being fired and seems to be a bit stronger, however it still snaps in half with minimal effort. What I used for a mold was one of those disposable foam square plates that have the plastic coating on them, so no water was siphoned from the test piece. 

On 8/12/2021 at 1:39 PM, Irondragon ForgeClay Works said:

I think the 1/4 inch thickness of the wafer may have contributed to the weakness also.

You're probably right about that. 1/4" seems WAY too thin for this refractory in particular. My ultimate goal is to line the rigidized kaowool in my drum barrel forge with the stuff, however it seems I may need to rethink how thick I need to make said lining. 

On 8/12/2021 at 1:10 PM, Buzzkill said:

You didn't mention the material of your mold form. In my experience anything that can wick moisture away from the kastolite when you apply it can result in a "crumbly" casting.  Any surface in direct contact with the kastolite should be damp/wet first.

Yea I noticed when I tried to get some of my new batch of kast-o-lite to stick to a small test piece of DRY rigidized kaowool, It wouldn't stick. It just kinda.. fell off. Well now I know that the contact surface has to be wet. Thanks!

On 8/12/2021 at 2:29 PM, Frosty said:

Welcome aboard Bootlegin, glad to have you. If you'll put your general location in the header you'll have a better chance of hooking up with experienced members living within visiting distance.

Frosty The Lucky.

First off, huge fan of your work an experimentation with zircopax and veegum. It's what inspired me to make my own furnace as well as experiment with my own mixtures! Also, thanks for the info on adding my general location. Ill do that once I figure out how. :P

Second, I had no idea that I had to actually compact the stuff so aggressively! I have just been pressing it with my fingers a bit. Sounds like that might be partially contributing to my test piece's weakness. I greatly appreciate all your advice!

Edited by Mod30
Trim quote.
Link to comment
Share on other sites

26 minutes ago, bootlegin said:

1/4" seems WAY too thin for this refractory in particular. My ultimate goal is to line the rigidized kaowool in my drum barrel forge with the stuff, however it seems I may need to rethink how thick I need to make said lining. 

1/4" is on the thin side, but remember that there's a difference between 1/4" supported by rigidized kaowool and 1/4" out there on its own. You can get away with a thinner layer on the sides and top of the forge chamber, while a thicker floor will stand up better to having workpieces getting plunked down on it.

Link to comment
Share on other sites

5 hours ago, bootlegin said:

First off, huge fan of your work an experimentation with zircopax and veegum.

That's Maarten in the Nederlands. Mike and I were really involved in the conversation but he was: making, testing and documenting all the test coupons.

If I make another propane forge I'll use a version for the flame face and nozzle blocks for the multi outlet burners. I've given a new forge a lot of thought and made drawings but I don't spend a lot of time in the shop anymore so don't know if it'd be worth the time and effort for something I may not do more than test. 

If you click on your Avatar or name at the top right of the page a menu will come up, select "edit profile" make the changes you want and save.  

My ribbon burner molds are from 1" x 4" lumber and a 2" x 6". The 2x6 is drilled for the crayons. The 1x4 is screwed and glued in two L sections that interlock and screw together. The rectangular form screws to the 2x6. All the lumber is sanded to baby butt fine and has several coats of epoxy spray appliance paint. When I cast a burner block I grease the dickens out of everything with some out of date vegetable shortning. The Kastolite still sticks to it, I have to pry the form sections apart.

I have about 30lbs. of Greencast 87 I used some years ago. It's a top shelf refractory but not a bubble refractory so has no better insulation properties than an equal thickness of limestone. Anyway, I sifted the aggregate out of a scoop and mixed it with enough water to make a latex paint texture and soaked some Kaowool in it to rigidize. 

I'd purchased commercial rigidizer and was experimenting to avoid the heart stopping expense of the "real" stuff with a silly short shelf life. 

Anyway, using the binder from a hard refractory as a rigidizer REALLY hardened up the Kaowool but lowered it's insulating properties. I've used fumed silica since and am happy with it.

When you apply a refractory or any similar . . . stuff you need to butter what you're putting it on. Buttering is a mason's term meaning to wet it. If you put any grout, cement, mortar, Kastolite, etc. on a dry surface the dry  surface will draw the moisture from the mix leaving a thin layer of dry powdery . . . junk. The mortar, etc. can't bond properly so the joint is weak and in forges will flake off. 

Applying a mortar to a buttered surface causes dilution at the contact point which wicks the binder in the mortar into all the nooks and crannies or along the fibers of Kaowool, where it hydrates and forms as strong a bond as possible.

So, always butter first!

Frosty The Lucky.

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...