Question on Kast-o-lite application: how long to wait after doing bottom to do too?

[Iswhatitis]

Hey guys!

 

I recently got to the point where I’m ready to apply kast-o-lite over the wool in my propane tank forge build. I sprayed the wool with rigidizer a few days ago and it is totally dry. I have read as much as I can find on putting kast-o-lite in forges but can’t find an answer to my question.

 

The way I have read is to apply it to the bottom of the forge, then flip it over after some period of time and do the top. I have also read about doing it in 3 sections. Here is my question: 

How long should I wait after doing the bottom to turn the forge upside down and do the top??

Also if I end up doing it in 3 sections is the time period I wait in between pieces the same or if different how long?

 

I saw that people recommended putting the whole thing in a bag after putting the kast-o-lite on for at least 24 hours before starting progressive fire drying cycles. One more question:

 

Do I wait 24+hrs and then cure between each section?

So in other words would I do the bottom section, wait 24 hours, then do progressive fire curing, then do the second section after the first is fully cured and so on?

Thanks for any insight you can provide!!

[Buzzkill]

I'm not sure what the "official" recommendation is, but here's what I do:   I set the shell so that I can cover the largest area possible without moving it.  Then I apply that largest section in one session.   Kastolite starts "firming up" as it sets fairly rapidly.  You need to be comfortable that the first part you cast won't fall off when you rearrange the shell for the next section. That can be even less than an hour sometimes.  Remember to wet (butter) the rigidized blanket before applying the Kastolite layer.

You don't necessarily need to turn it completely upside down.  You may be able to turn it halfway one direction, then halfway the other direction so you can apply to the blank spots without gravity pulling the previous section straight down.

I usually wait a couple hours or resume the next day.   I don't know with absolute certainty, but my impression is that subsequent applications of Kastolite will bond better to previous applications if they are still damp, but solid. As others have mentioned elsewhere, I find I get the best results by "patting" Kastolite with a trowel, putty knife, or even rubber gloved hand.  That tends to pack it into place better and pushes the rough edges down past the surface.

I do not recommend firing until all the Kastolite has been applied.

[Irondragon Forge ClayWorks]

I agree do not fire it to cure between applications. We did our forge in two applications, bottom and half way up the sides first, waited 24 hours then did the top and remainder of the sides then fired it after another 24 hours.

[Iswhatitis]

Thank you to both of you guys.

Buzzkill: when you talk about turning one way then turning the other way, are you saying to apply it in 3 different sections? In other words do it in thirds? Also when I wet the ceramic wool, how wet does it need to be? Should I just mist it a bit or should I get it pretty wet?

Also how much water did you mix with each pound of kast-o-lite? Or did you just mix it by eye?

 

Dragon: how much water per pound did you use if you didn’t just eye ball it? How much did you wet your ceramic wool before applying the kast-o-lite?

 

Thanks a ton guys! I have a couple pounds of bubble alumina I plan to put on just the bottom over the kast-o, and then i have that it-100 stuff or something like that to put on everywhere last. 
 

This will be amazing when it is done. I have been using a shitty coffee can forge with terrible insulation for like six months and the difference this forge will probably  make will probably be shocking.

[Buzzkill]

You can still do it in 2 sessions if you turn it one way and cover what gravity will allow then turn the other way and meet in the middle so to speak - or you can do it in 3 separate applications.  Either method will work.

The surface of the blanket should be quite damp, but not have standing water on it or anything.  The bottom line is you don't want the blanket wicking water away from the Kastolite.  The water in it is needed for it to cure properly.

I mix Kastolite by eye/feel.  There is a fairly narrow range of water between too dry and too wet.  I usually get it a little too wet intentionally to begin with so that it mixes well and then I sprinkle on a little dry product, mix, and then add more and repeat as needed until I get the consistency I'm looking for.

You don't really need the additional bubble alumina on top of the Kastolite, but it shouldn't hurt anything.  It might make your heat up time slightly longer is all.

If you have a properly sized, built, and tuned burner for the forge it should be a nice change for you.  If nothing else you should have a little more space to work with.

[JHCC]

A few things:

1. Don't just let the rigidizer dry; you actually have to fire it and bring it up to a glowing heat, so that it will fuse to the kaowool.
2. Kastolite takes 2.75 oz of water per pound of dry mix. I measure both with a kitchen scale. When mixed up, this will look MUCH too dry, but it will be fine.
3. On my first forge, I did the Kastolite in three sections. It worked, but wasn't idea. My most recent forge, I built a form to match the desired inside cavity and rammed the Kastolite in around that. Worked great.

[Iswhatitis]

Awesome replies thank you. I wasn’t aware that rigidizer had to be fired because none of the forge building instructions I read said anything about firing it with just wool and rigidizer. It’s now very dry and I wonder if it is too late to do it at this point. 
 

Buzzkill: I don’t think it will take longer to heat up because of a thin layer of bubble alumina especially since I am putting the reflective coating over it but if it does it hopefully won’t be a big deal. My reason for using it is that according to my research it is even a good bit more flux resistant than just kastolite so I felt that I would be able to go longer without having to patch the forge from wear as a result of welding but the sources I got this information from also didn’t say anything about firing the rigidizer right after applying it to the wool.

 

jhcc: do you think it is worth trying to fire the rigidizer itself at this point? It has been dry for about a week. When I applied it it soaked into the wool and didn’t just sit on the surface so it seems like it should hopefully be ok. The container doesn’t say anything in the directions about firing it, it just says to let it dry at room temperature and that if you want to you can expose it to 150 degrees F to help it dry faster. If it was mandatory you would think they would put it in the directions but I wouldn’t put it past them to leave it out.

I’m assuming the reasoning behind firing the rigidizer must have to do with improving the adhesion of the castable refractory because once the kastolite is on, it should prevent any particles of wool from becoming airborne. 

[pnut]

Yes, heat up the rigidized wool. It doesn't matter if it's been a week. One other thing, before you apply the Kast o Lite you should spritz the wool with a spray bottle.

Pnut

[JHCC]

If the rigidizer is fumed silica (most are), then firing it will make the whole thing much more durable. Go for it.

[Iswhatitis]

Ok guys thanks so much! Today I fired the rigidizer for a bit and now I am going for application 1 of 2 of kastolite. I’ll let you know how it goes.

[Iswhatitis]

So I put the KOL on the bottom half and now am finding conflicting info on whether I should flip it ina few hours once it firms up and do the top, or whether I should give it 24 hrs before flipping it.

 

I also have a question: should I put it in the plastic bag with the wet towel while I wait for it to get firm enough to flip or do I wait until the whole thing is cover in the KOL to put it in the bag???

 

 

[JHCC]

Once the water hits the dry mix, the chemical reactions start, so once you finish putting the KOL in place, it's time for curing in the high-humidity environment. If it's firm enough to flip now, go ahead with doing the top and then bag it. If you're not going to be able to get to it for a while, bag it in the meantime.

[Iswhatitis]

Awww man I used bad language again so I guess they have to check my posts before anyone sees them, sorry mods! It’s a hard habit to break I apologize for breaking the rules. 
 

I did end up bagging it and there is a nice fine condensation on the inside of the plastic bag so I’m glad you confirmed that was the correct thing to do. It should actually be firm enough now to flip and do the top so I will most likely get that done in the next couple of hours so I can let it chill in the bag for a full 24 before I start progressive firing. Thanks again for your awesome expert help JHCC, I’m someone who wants to things as correctly as I can the first time so my result is at least decent despite me being a total noob so having you guys to ask about this stuff is a relief. I’m also pretty slow to understand things sometimes even when it’s spelled out for me so thanks again!

[ThomasPowers]

Don't worry about being moderated; most of us have had it happen a time or two---I've been moderated for a typo before! (And I was once moderated for a phrase I had used speaking to my Pastor the previous Sunday in Church!)  Just try to do better and remember we are trying to run the site so we can suggest it to young children or elderly Aunts with no fear of them running into something that will give them palpitations!

When there are problems is when folks get all defensive and abusive, I guess they don't realize that they are NOT paying to have this site on the web and so don't get to make the rules;  shoot I donated to help keep this site on the web and I don't get to make the rules either!

[Iswhatitis]

It’s also just such a valuable resource of people passionate about blacksmithing who all together have a huge base of knowledge and are willing to help people and give knowledge freely. Even if it hurts a bit to try to modify my communication it’s worth it. Not to mention the blueprints.  Speaking of I am going to make some of those tongs in one of uri hofi’s blueprints which can hold an amazing variety of stock. 

[Iswhatitis]

Hey guys I just wanted to update to say that I finished her to the point where I have been using her. Thank goodness for all the great info and advice on this site because it is insane how much better this forge is compared to my noob plaster perlite sand in a paint can forge! 
 

anyway here is a couple pictures:

 

I still have yet to build the brackets that the bricks will sit on but I will do it once I go and get some angle iron this weekend. Thank you all! 

 

 

[Frosty]

Looking pretty HOT from here. 

Frosty The Lucky.

[Iswhatitis]

Thanks man and thank you for developing these burners! They are way hot! I can turn this bad boy to 5 psi and flick on both burners for a bit to heat up the forge, then I can cut one off and use one burner still at 5psi to forge regular stuff. I haven’t tried welding in it yet but I can tell this bad boy will weld like a champ!

[Frosty]

You're welcome, it's my pleasure. Enjoy using it but be aware just having a HOT forge doesn't mean a fellow won't be welding like a CHIMP instead.  

Let the fun begin!

Frosty The Lucky.

[Murfski]

This is my first post here, so please cut me some slack if I'm asking a question that someone has already answered.  This is the best topic I could find to ask my question.

I've not used Kast-o-Lite before; I've been using Satanite. With that stuff, I mix it to the texture of a thick paint, and paint it onto the wool insulation.  I do several coats, and usually build it up to about 1/4 inch.  It's kind of a pain, and it takes a while for the first coat(s) to dry before painting on subsequent coats, but it does work well.  My question is: Will this method work with Kast-o-Lite?  I've had good results with the Satanite for a number of years, but after reading some of the comments about Kast-o-Lite here, I want to try it out.

Any advice will be appreciated.

[Buzzkill]

No, that will not give you good results with Kastolite.   It should seem almost too dry when it's mixed properly. If you squeeze a handful it should retain the shape without any water dripping out of it.  The manufacturer ratios of water to dry mix are what you should use.  I personally hold back a little bit of the dry mix, add all the water to the majority of the mix, stir until the water is well distributed, then add the last bit of dry mix and stir again until thoroughly mixed before application.

It doesn't even trowel well.  For me the best method has been to wet the surface I'm applying it to, then drop roughly a handful of material where I want it, then pat it gently but firmly using either a putty knife or a rubber (or nitrile) gloved hand to get the desired thickness and to get a nearly smooth outer surface.  It is water setting, so you have a limited amount of time after mixing to work it into place before it starts to harden up. You don't have to rush it, but you can't wait an hour after mixing before application.

[Buzzkill]

If you plan to use flux I suggest you use a sacrificial removable slab on the floor.  Kastolite is somewhat flux resistant, but over time it can turn into a gooey sticky mess at welding temps if it has been exposed to a lot of flux.   High alumina kiln shelf has been recommended by some.  Split hard firebrick is something I've also seen recommended. A stainless tray filled with kitty litter has been suggested before as well.

[Tooln]

I've been reading this to learn about Kast-O-Lite as I soon be doing my forge.  My question is more about rigidizer, do you really need to do it and what are the benefits of using if you do.  I asked this question to my wool supplier and was told it didn't need to be done.  I do understand it will bond the fibers but if your covering with Kast-O-Lite what's the purpose.  Thanks for the answers, I've been getting a lot of help information here.  

[Frosty]

I've asked a few folks about rigidizing the ceramic blanket refractory they sold ad not one said it did much if any good. However when I asked the guys who use it, HVAC service men they said rigidizing ceramic blanket made it last longer. The vitrified fibers tend to be very brittle and when furnaces turn on there is a bit of a shock wave when the fuel lights. The whoosh flexes the fibers and they break off.

If you're going to encapsulate blanket with a hard castable refractory it won't escape into your breathable air. However I find rigidized blanket is easier to coat with hard castable refractory, Kastolite has crushed aggregate in it so it does NOT move easily with a trowel or by spanking into position. Spanking (slapping it with my hand or a spatula) seems to be the most effective but if the blanket moves easily the castable doesn't. 

Lastly if the base, Kastolite 30 in this case, resists movement in use the castable refractory flame face is more durable. Once set and cured hard refractories are like unreinforced concrete, tremendous compressive strength but very little bridging strength, it does NOT like being flexed so it cracks and can break.

Make sense?

On a last note, I've found counter personnel are concerned with sales so of course THEIR product doesn't need help performing! It doesn't make them bad folk or dishonest, their job is to know: what, where, how much and when it can be there. The service guys are the ones to tell you how to work with it. It's like asking a car salesman how to adjust a transmission that's slipping.

Frosty The Lucky.