Hardening a piece of armor is an important step in ensuring it will last beyond the first few days of its creation. Pepakura in particular is at risk for damage because before hardening it is primarily composed of Cardstock. Before hardening, it is important to perform a Resining coat on the piece first to give it a critical extra bit of strengthening. Hardening cardstock without a layer or two of resin can make it much more likely to warp or collapse.

Basic Procedure[edit | edit source]

In general, all hardening methods are performed on the inside of the armor piece. This is because hardening tends to obscure details and if it were sanded after being placed on the outside, it would lose its strength.

To harden, a material must be selected and then applied to the inside of the armor. Each hardening choice has its benefits and drawbacks which are outlined below. For information on other theoretical or uncommonly used methods, read Alternative Hardening Methods. This list ranks the efficacy of the options based on key factors on a scale of one to five. There are stronger or cheaper etc materials out there (some of which are covered in the Alternative Hardening Methods), but this is a pragmatic list of options that directly relate to armoring and are well tested. 5 means good, 1 means bad.


The best strength to weight ratio (4:1) of the three, fiberglass involves laying down strips of resin soaked fiberglass inside. Its main drawback is sanding into it from the outside (to cut detail lines on the armor or sanding) reduces its strength, and any hard corners or indents inside the armor will turn into air bubbles with fiberglass, which can be popped accidentally from the outside creating ugly holes.

  • Strength: 4
  • Weight: 5
  • Modifiability: 2


The easiest method for hardening, rondo involves mixing resin and bondo together with catalyst and pouring it inside the armor. This easily and quickly covers the inside with a layer and can be used to reach dificult areas and is also easily sandable/cuttable from the outside for detailing. It suffers from a very poor strength to weight ratio (1:1), meaning it is incredibly brittle and heavy, so dropping or leaning on a rondo-only piece can crack it more easily than the other methods.

  • Strength: 3
  • Weight: 3
  • Modifiability: 5

Rondo Fiberglass Hybrid

A method of increasing the weight of the piece a little, this method can be used to take advantage of the benefits of the previous two methods while suffering from none of their drawbacks (except weight). The method involves pouring a thin layer of rondo first to cover edges and indents, and then reinforcing that with two to three layers of fiberglass. A third layer consisting of rondo can be then poured to smooth the fiberglass (thereby protecting the wearer from potential prickles from the fiberglass).

  • Strength: 5
  • Weight: 2
  • Modifiability: 4

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